When do babies get shy with strangers?
The CDC's milestone checklist lists “Is shy, clingy, or fearful around strangers” by 9 months, and “Reacts when you leave (looks, reaches for you, or cries).” So shyness with new people is on the CDC's list of what most babies (75% or more) do by 9 months. If you're worried about how your baby reacts to people, talk with your pediatrician.
Checked October 29, 2026.
What the CDC's checklists say
| By | The CDC's milestone | Month page |
|---|---|---|
| 6 months | Knows familiar people | Your baby at 6 months |
| 9 months | Is shy, clingy, or fearful around strangers | Your baby at 9 months |
| 9 months | Reacts when you leave (looks, reaches for you, or cries) | Your baby at 9 months |
Each row is from the CDC's checklist for that age (6 months, 9 months), checked October 29, 2026.
What “by 9 months” means
Developmental milestones are things most children (75% or more) can do by a certain age. The CDC puts each milestone at the age by which at least 75% of children would be expected to do it, so that even one missing milestone leads to a conversation with the doctor instead of “wait and see”. So “by 9 months” isn't an average. Many children do it sooner, and the checklists don't list everything a child learns.
What it can look like
Clinging to you, turning away or crying when someone new comes close, and fussing when you leave the room.
What helps
- Let new people warm up slowly: hold your baby while the visitor talks to you first.
- Say goodbye when you leave, even for a minute, and hello when you come back.
- Play peekaboo. Going away and coming back is the whole game.
Talk to your pediatrician if…
Your baby isn't doing this by 9 months, the age on the CDC's list, has lost a skill they once had, or you're worried for any reason.
You know your child best. Don't wait. If your child is not meeting one or more milestones, has lost skills he or she once had, or you have other concerns, act early. Talk with your child's doctor, share your concerns, and ask about developmental screening.
If you or the doctor are still concerned, the CDC says to ask for a referral to a specialist, and to call your state's early intervention program (find the number on the CDC's list). You do not need to wait for a doctor's referral or a medical diagnosis to make this call. If your child is younger than 3 years old, contact your local early intervention system.
More from the CDC: Concerned about your child's development? If your child seems unwell, call your pediatrician, or 911 in an emergency.
Sources
- CDC, Milestones by 6 months (Learn the Signs. Act Early.) (checked October 29, 2026)
- CDC, Milestones by 9 months (Learn the Signs. Act Early.) (checked October 29, 2026)
- CDC, Key Points about CDC's Developmental Milestone Checklists (checked October 29, 2026)
- CDC, CDC's Developmental Milestones: Concerned about your child's development? Act early. (checked October 29, 2026)
- CDC, Concerned About Your Child's Development? (checked October 29, 2026)