The 15-month sleep regression typically lasts 1 to 2 weeks. It’s a temporary disruption, not a permanent change in your toddler’s sleep abilities. Sleep skills don’t disappear at specific ages, so while the rough patch can feel endless at 2 a.m., your child’s previous sleep patterns will return.
That said, the 15-month mark sits at a crossroads of several developmental changes happening at once. Understanding what’s driving the disruption helps you respond in ways that don’t accidentally extend it.
Why Sleep Falls Apart Around 15 Months
Three things tend to collide at this age, and any combination of them can explain why your toddler is suddenly fighting bedtime, waking at night, or refusing naps.
Separation anxiety: Many toddlers who sailed through infancy without separation issues start showing them for the first time around 15 to 18 months. As your child develops more independence during the day, they become more aware of separations, and bedtime is the biggest one. The protests are often loud, tearful, and hard to interrupt. Separations feel worse when kids are tired, hungry, or sick, which covers a lot of toddlerhood.
Teething pain: First molars typically erupt between 13 and 19 months. Unlike the smaller front teeth, molars have a broad surface that puts more pressure on swollen, tender gums. If your child is drooling more than usual, chewing on everything, or fussy during the day (not just at sleep times), teething is likely playing a role.
Cognitive leaps: At 15 months, toddlers are processing new motor skills like walking and climbing, building vocabulary, and testing boundaries. A brain buzzing with new abilities has a harder time powering down for sleep. You may notice your child “practicing” skills in the crib instead of settling.
Sleep Regression vs. the Nap Transition
This is the question that trips up most parents. Around 15 months, many toddlers start resisting their second nap, and it’s easy to assume they’re ready to drop to one nap. Sometimes they are. But often, the regression is mimicking nap-transition readiness, and switching to one nap too early makes everything worse.
Signs your child genuinely needs to drop to one nap include consistently resisting or skipping the second nap, taking shorter naps than usual, waking unusually early in the morning, or lying awake for long stretches in the middle of the night. If your child is regularly getting less than 10 hours of overnight sleep on a two-nap schedule, shifting to one nap may actually help lengthen nighttime sleep.
The key word is “consistently.” If these signs have only been happening for a few days, you’re more likely dealing with the regression. Give it the full 1 to 2 weeks before making permanent schedule changes. Most toddlers aren’t truly ready for one nap until closer to 15 to 18 months, and some not until later.
How Much Sleep Your 15-Month-Old Needs
Toddlers between 12 and 24 months need 11 to 14 hours of total sleep per day, including naps. During the regression, your child will likely fall short of that range on some days. That’s normal and temporary. What matters more than hitting an exact number is maintaining the routines that help sleep bounce back once the regression passes.
What Actually Helps During the Regression
The most effective approach is simple: stay consistent with your existing routines and avoid introducing new sleep habits you’ll need to undo later. If your child was falling asleep independently before the regression, try to preserve that as much as possible. Every regression ends faster when you don’t layer on new associations like rocking to sleep or bringing your toddler into your bed for the first time.
That doesn’t mean leaving your child to scream. Responsive settling at this age can include sitting beside the crib and comforting your child with your voice, or briefly patting or rubbing their back while they work on calming down. The goal is offering reassurance without taking over the process of falling asleep entirely.
A consistent bedtime routine is your strongest tool. About 20 minutes of quiet, predictable activities before bed, done in the same order at roughly the same time each night, signals to your toddler’s brain that sleep is coming. This matters even more during a regression, when everything else feels unpredictable to them.
If you do end up providing more hands-on comfort during the worst nights, you can scale it back gradually once the regression passes. Move from whatever settling method you used to something slightly less intensive, waiting until your child adjusts before pulling back further. For example, go from rocking to sleep to rocking until drowsy, then from drowsy rocking to just sitting nearby.
When It Lasts Longer Than 2 Weeks
If sleep hasn’t improved after about 2 weeks, something else is likely going on. The most common culprits are an underlying schedule problem (too much or too little daytime sleep), ongoing molar pain, or an ear infection that developed alongside teething. Persistent night waking beyond 2 weeks can also signal that a new sleep association formed during the regression and your child now expects that help every time they wake.
It’s also worth reconsidering the nap transition at this point. If your toddler has been fighting the second nap for 2 or more weeks straight, that pattern is no longer a regression. It’s a genuine readiness signal, and adjusting the schedule will likely resolve the sleep issues faster than waiting it out.