At 21 months so much is falling into place with your toddler every day—from new motor skills to new words to new comprehension skills. Expect your heart to swell with pride one moment…and then your blood pressure to raise the next when they push limits! 

Your 21-Month-Old Child’s Development

Many toddlers are already demonstrating the behaviors that are lumped under the “terrible twos” category. But, this isn't them being terrible—really! It’s them learning to cope with their larger-than-life emotions, further developing a sense of self, and expressing their desire for personal control. In other words, they are well on their way to managing themselves as independent human beings. (Even if it doesn’t feel like it right now!) 

Toddlers also experience a big verbal boom between the ages of 18 and 24 months. Don’t expect them to speak full, grammatically correct sentences, but do listen for new words on a regular basis and encourage your child to start stringing them together for simple sentences, such as “me ball” or “Mama water.” 

21-Month-Old Developmental Milestones

There’s not an official list of 21-month-old milestones, but your pediatrician will be assessing your tot’s development in a few months at their 24-month checkup. Below are the milestones that are on the horizon for 24 months (and you can refresh your memory on 18-month milestones here). Just keep in mind that there’s a big range of what’s considered developmentally “normal”—some kids hit milestones “early” and others hit them “late.” If you have any questions about your child’s development, your care provider will be your best resource! 

Upcoming Milestone Checklist

  • Noticing when others are hurt or upset
  • Pointing to proper objects in a book when you ask
  • Stringing at least two words together, like “more milk”
  • Pointing to at least two body parts when you asked
  • Making gestures beyond waving and pointing
  • Holding something in one hand while using the other hand
  • Attempting to use switches, knobs, or buttons on a toy
  • Playing with two or more toys at the same time
  • Kicking a ball
  • Running
  • Walking (not climbing on all fours) up a few stairs with or without help
  • Eating with a spoon

Your 21-Month-Old’s Growth

On the physical development front, your toddler is probably looking the part these days. With the average 21-month-old boy weighing about 25 pounds and stretching 33.5 inches tall and the average 21-month-old girl hitting 33 inches and 24 pounds, it may seem like your little one is transforming before your eyes from a baby into a child. The combination of more muscle control and more desire to test the limits may have them running, jumping, or climbing on anything they can—or not! Many completely capable kids are also naturally cautious.

Your 21-Month-Old and Teething

Your 21-month-old’s mouth is filling up…but they aren’t done yet! There are still tiny teeth waiting to erupt, which could explain fussy behavior. Here are some teeth that your little one might be working on now—or very soon (see the complete teething schedule):

  • Between 16 and 22 months: upper canine (cuspid) erupts 
  • Between 17 and 23 months: lower canine (cuspid) erupts 
  • Between 23 and 31 months: second lower molar erupts
  • Between 25 and 33 months: second upper molar erupts

For help soothing your tot’s discomfort, here’s more on teething. And while you’re at it, peep our guide to safely dosing toddlers with pain relievers

Your 21-Month-Old’s Behavior: Think Like a Toddler

It can seem like toddlers are ruled by extremes. We should give them more credit than that, though. They can also be quite nuanced: Maybe your little one generally loves running around, but jumps into your lap for a snuggle when they are scared. Or maybe they are reserved around other people, but extremely chatty in the comfort of their home. Take the time to appreciate all that makes your child so wonderful.

As unique as they are, there are also some strategies that work almost universally on influencing toddlers—like some healthy reverse psychology. For example, say your eater has now developed some pickier habits that you want to nip in the bud. Continue serving them a well-balanced plate of options. Then when you all sit down around the table, start asking for some veggies (or whatever they are resisting) from their plate. Put your acting skills on display by pretending it’s your favorite food in the world! There is a good chance that will make them think, “Hey, if it’s so good, then I’m going to keep it for myself.” 

If your child is exhibiting some aggressive behaviors—like biting, hitting, or pulling hair—another successful strategy is to focus your attention on the victim. There are many reasons toddlers can physically lash out, including limited verbalization skills, next to no impulse control, and a desire for attention. You can address all of that at the same time this way: If your child hits, openly sympathize with the person (or animal) who was hit by comforting them, saying hitting makes you sad, and sharing that you want your child to use their words—all while your child eavesdrops (remember reading about gossiping to encourage good behaviors? Well, gossiping can help correct negative behaviors too!). 

Your 21-Month-Old Child and Sleep

Your child’s sleep schedule has come a long way from the earliest months of life. But, now you may be facing some new bedtime dilemmas. Around this point, many parents wonder whether they should transition their child from a crib to toddler bed. The right time ultimately comes down to your child’s readiness. (The exception: If they are climbing out of their crib, it’s time to make the switch…pronto!) You can help set the stage for a successful move by setting up a toddler bed in their room for use during naptime or resting. And talk up their new bed! Sing silly songs about the “big kid bed,” pick out special sheets together, gossip about how exciting it is… They’ll pick up on that!

The next part of the challenge: Getting them to stay in bed. If you’ve given them a chance and found they want to roam back out of the room after lights are out, put a baby gate on the door and explain “big kids stay in bed.” It may take a few nights (or more), but consistency on your side will pay off. 

If you’ve been bed sharing and want to reclaim the space, ease into it by getting them more excited about their own bed, building their alone-time confidence, and acting out bedtime with dolls. At night, it may help to sleep beside your child’s bed for a few nights. Once they’ve become comfortable with that, begin to leave the room, but check back in while they are falling asleep, so they know you’re still nearby. 

Sleep Regression at 21 Months

Parents are often warned about baby sleep regressions…but unfortunately sleep can regress in toddlerhood too. Teething, developmental changes, and growth spurts can all disrupt precious ZZZs. Learn more about toddler sleep regressions

Your 21-Month-Old’s Health: Constipation, Diarrhea, and Other Tummy Troubles 

What do toddlers and their tummies have in common? Both can be very temperamental! From stomach bugs to constipation and everything in between, tummy troubles can be part of life with toddlers. Here’s what to know...

  • Because their vocabularies are still limited, your toddler may not be able to describe exactly how they are feeling. Signs their tummy is giving them trouble include bloating, gas, diarrhea, or vomiting. Here’s how to decode your toddler’s bellyaches.
  • If tummy troubles occur regularly, take note of what your child is eating. To combat constipation, try to up their fiber intake and ensure they are hydrated. These foods can help prevent and ease constipation
  • Vomiting and diarrhea often go together. If your child experiences vomiting and/or diarrhea that lasts more than one day or there is blood in it, hustle to the doctor’s office right away. Not only are these symptoms of larger issues, but dehydration also becomes a concern if your kiddo can’t keep fluids down. More on how to help a toddler with vomiting.


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  • The Happiest Toddler on the Block, Dr. Harvey Karp, MD
  • Centers for Disease Control and Prevention: 2-Year Milestones
  • American Speech-Language-Hearing Association: Speech Development One to Two Years
  • Centers for Disease Control and Prevention: WHO Growth Charts
  • American Dental Association: Teeth Eruption Charts

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Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.