Toddler Is Aggressive Toward Baby Sibling
Medically reviewed by Dr. Emily Torres, PhD, CCC-SLP · Pediatric Speech-Language Pathologist
Content reviewed against published AAP, Zero to Three, CDC guidelines
Last reviewed:
Behavioral development varies greatly from child to child. If you have noticed toddler is aggressive toward baby sibling, here is what you need to know.
The short answer
Aggression toward a new baby sibling is common and does not mean your toddler is a bad child or will always be aggressive. Your toddler is experiencing huge emotions about sharing you - jealousy, confusion, loss of their previous position, and fear of being replaced. They lack the maturity to express this verbally, so it comes out physically. Never leave your toddler unsupervised with the baby, and address the underlying emotions with empathy.
Key takeaways
- Aggression toward a new baby sibling is common and does not mean your toddler is a bad child or will always be aggressive. Your toddler is experiencing huge emotions about sharing you - jealousy, confusion, loss of their previous position, and fear of being replaced. They lack the maturity to express this verbally, so it comes out physically. Never leave your toddler unsupervised with the baby, and address the underlying emotions with empathy.
- Usually normal when: Some aggression toward a new sibling is very common
- Call your doctor if: Your child has injured the baby
- Varies by age — see the age-by-age breakdown below
This is one of the most common questions parents ask. Searching for answers means you care.
What Parents Should Know
According to AAP, Zero to Three, CDC guidelines, aggression toward a new baby sibling is common and does not mean your toddler is a bad child or will always be aggressive. Your toddler is experiencing huge emotions about sharing you - jealousy, confusion, loss of their previous position, and fear of being replaced. They lack the maturity to express this verbally, so it comes out physically. Never leave your toddler unsupervised with the baby, and address the underlying emotions with empathy. At 12-24 months, a young toddler may not understand the baby is fragile. They may poke, squeeze, or hit the baby out of curiosity or because they have seen you touch the baby. Supervise all interactions, model gentle touch, and guide their hands: "Gentle. Like this. Soft touches for baby.". It is generally considered normal when some aggression toward a new sibling is very common. However, you should contact your pediatrician promptly if your child has injured the baby.
Normal vs. Concerning
By Age
What to expect by age
12-24 months
A young toddler may not understand the baby is fragile. They may poke, squeeze, or hit the baby out of curiosity or because they have seen you touch the baby. Supervise all interactions, model gentle touch, and guide their hands: "Gentle. Like this. Soft touches for baby."
2-3 years
Aggression may be more intentional as your toddler processes jealousy. They understand that you pay attention to the baby and may hit the baby to express frustration. Validate feelings: "It is hard to share mommy. You love mommy so much." Set firm limits on behavior: "I will not let you hurt the baby."
3-4 years
Your child can understand more. Talk about what it is like to have a sibling. Create special one-on-one time with your toddler. Involve them in baby care in safe ways (bringing diapers, singing to baby). Praise all gentle interactions enthusiastically.
4-5 years
Aggression toward the baby should be decreasing. If it persists, your older child may need more individual attention and support processing their feelings. Consider whether the sibling dynamic involves other issues like parental favoritism (even unintentional) that need addressing.
What to Tell Your Pediatrician
- Describe when you first noticed toddler is aggressive toward baby sibling and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if aggression toward the baby is increasing over time.
- Mention if your child seems to target the baby specifically and deliberately.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Some aggression toward a new sibling is very common
- Your child is also showing curiosity or affection toward the baby
- Aggression decreases with time, attention, and consistent limits
- Your child is not aggressive in other settings
- Aggression toward the baby is increasing over time
- Your child seems to target the baby specifically and deliberately
- You are unable to keep the baby safe even with supervision
- Your toddler shows no positive interest in the baby after several months
- Your child has injured the baby
- You are afraid to leave your children in the same room for even a moment
What You Can Do at Home
- Keep track of when you notice toddler is aggressive toward baby sibling — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that some aggression toward a new sibling is very common — this is generally within the range of normal.
- At 12-24 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Respond consistently and calmly to your baby's behavior. Maintain predictable daily routines.
- While monitoring at home, seek immediate care if your child has injured the baby.
Related Conditions
How Long Does It Take a Toddler to Adjust to a New Baby?
Most toddlers take 3-6 months to fully adjust to a new sibling, though some take up to a year. The first few weeks often involve a "honeymoon" period where everything seems fine, followed by regression and acting out as the reality sets in. This is completely normal. Your toddler's world has fundamentally changed, and they need time, patience, and extra connection to adjust.
Teaching Toddlers Gentle Hands and Gentle Touch
Teaching "gentle hands" is one of the most important and most repeated lessons of the toddler years. Young children genuinely do not understand their own strength or that their actions cause pain. Gentle touch must be actively taught and demonstrated hundreds of times. It is a skill that develops gradually through patient, consistent modeling and practice - not through punishment.
Toddler Hits When Angry or Frustrated
Hitting is one of the most common toddler behaviors and is developmentally normal between ages 1-3. Your toddler hits because their emotions are bigger than their ability to manage them, and physical expression is their most available tool. Hitting does not mean your child is aggressive or that you are failing as a parent. Respond by calmly stopping the behavior, naming the emotion, and teaching alternatives over many, many repetitions.
Behavioral Regression in Toddlers
Behavioral regression - when your toddler temporarily loses skills or returns to earlier behaviors - is common and usually temporary. It often happens during stress, big changes, developmental leaps, or illness. Your child has not lost their skills; they are temporarily unable to access them because their brain is processing something new or stressful. With patience and support, skills return.
Related Resources
Frequently asked questions
Is toddler is aggressive toward baby sibling normal?
When should I call the doctor about toddler is aggressive toward baby sibling?
When is toddler is aggressive toward baby sibling normal?
What causes toddler is aggressive toward baby sibling?
What should I mention to my pediatrician about toddler is aggressive toward baby sibling?
Is toddler is aggressive toward baby sibling normal at 12-24 months?
Is toddler is aggressive toward baby sibling normal at 2-3 years?
Should I go to the ER for toddler is aggressive toward baby sibling?
Does toddler is aggressive toward baby sibling go away on its own?
References
- [1]American Academy of Pediatrics. Preparing Your Child for a New Sibling. HealthyChildren.org. AAP
- [2]Zero to Three. The New Baby: Helping Your Older Child Adjust. Zero to Three
- [3]Centers for Disease Control and Prevention. Positive Parenting Tips. CDC
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Toddler Is Aggressive Toward Baby Sibling.
Things to mention
- Describe when you first noticed toddler is aggressive toward baby sibling and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if aggression toward the baby is increasing over time.
- Mention if your child seems to target the baby specifically and deliberately.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Aggression toward the baby is increasing over time
- Your child seems to target the baby specifically and deliberately
- You are unable to keep the baby safe even with supervision
Urgent signs to report immediately
- Your child has injured the baby
- You are afraid to leave your children in the same room for even a moment
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of toddler is aggressive toward baby sibling are normal. Talk to your pediatrician if your child has injured the baby.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
Was this page helpful?
Related Behavior Concerns
How Long Does It Take a Toddler to Adjust to a New Baby?
Most toddlers take 3-6 months to fully adjust to a new sibling, though some take up to a year. The first few weeks often involve a "honeymoon" period where everything seems fine, followed by regression and acting out as the reality sets in. This is completely normal. Your toddler's world has fundamentally changed, and they need time, patience, and extra connection to adjust.
Teaching Toddlers Gentle Hands and Gentle Touch
Teaching "gentle hands" is one of the most important and most repeated lessons of the toddler years. Young children genuinely do not understand their own strength or that their actions cause pain. Gentle touch must be actively taught and demonstrated hundreds of times. It is a skill that develops gradually through patient, consistent modeling and practice - not through punishment.
Toddler Hits When Angry or Frustrated
Hitting is one of the most common toddler behaviors and is developmentally normal between ages 1-3. Your toddler hits because their emotions are bigger than their ability to manage them, and physical expression is their most available tool. Hitting does not mean your child is aggressive or that you are failing as a parent. Respond by calmly stopping the behavior, naming the emotion, and teaching alternatives over many, many repetitions.
Behavioral Regression in Toddlers
Behavioral regression - when your toddler temporarily loses skills or returns to earlier behaviors - is common and usually temporary. It often happens during stress, big changes, developmental leaps, or illness. Your child has not lost their skills; they are temporarily unable to access them because their brain is processing something new or stressful. With patience and support, skills return.
Bonding and Attachment Timeline for Adopted Babies
Bonding with an adopted baby is a real and achievable process, but it may follow a different timeline than biological bonding. Many adoptive parents feel a strong connection quickly, while for others it develops gradually over weeks or months. Consistent, responsive caregiving is the single most important factor in building secure attachment, regardless of how your family was formed.
Aggressive Play vs Normal Play
Rough-and-tumble play — wrestling, chasing, play-fighting, and superhero battles — is a normal and important part of child development, particularly for toddlers and preschoolers. It helps children develop physical coordination, social skills, self-regulation, and an understanding of boundaries. The key distinction between normal rough play and concerning aggression is whether both children are having fun, there is turn-taking in roles, and no one is intentionally trying to hurt the other.