Yes, many toddlers experience a noticeable disruption in sleep around 15 months. It’s not a single dramatic event but a convergence of developmental changes that can make a previously good sleeper suddenly resist bedtime, wake during the night, or fight naps. The good news: it typically lasts one to two weeks when you stay consistent with sleep habits.
Why Sleep Falls Apart at 15 Months
The 15-month sleep regression isn’t driven by one thing. Several developmental shifts tend to collide around this age, and together they can make sleep feel like it’s unraveling. The biggest culprit is usually the nap transition. Between 12 and 15 months, most toddlers are ready to drop from two naps down to one. If your child is still on a two-nap schedule, they may have simply outgrown it. Their body doesn’t need as much daytime sleep as it used to, so the extra nap creates too little sleep pressure at bedtime or causes overnight waking.
At the same time, first molars are often pushing through. These larger teeth typically erupt between 13 and 19 months and can cause discomfort that makes it harder to fall asleep or stay asleep. Layer on the fact that many toddlers hit a peak in separation anxiety right around 15 to 18 months, and you have a recipe for bedtime battles. Some toddlers who never showed separation anxiety as infants start displaying it for the first time at this age, with loud, tearful protests when a parent leaves the room.
Signs It’s a Nap Transition, Not Just a Phase
A lot of what looks like a sleep regression at 15 months is actually your toddler telling you their schedule needs to change. The signs that a nap transition is the real issue include:
- Refusing or protesting one of their naps
- Taking more than 20 minutes to fall asleep at naptime or bedtime
- Naps getting shorter even when the schedule hasn’t changed
- Early morning waking that wasn’t happening before
- New overnight waking when nights had been going well
If you’re seeing several of these at once, your toddler likely needs to move to a single midday nap rather than two shorter ones. This transition can feel rocky for a week or two as their body adjusts, but it often resolves the nighttime disruptions on its own.
How Much Sleep a 15-Month-Old Needs
Toddlers between 1 and 2 years old need 11 to 14 hours of total sleep per day. At 15 months, napping typically accounts for 1 to 2 hours of that total. Two naps per day are normal at the younger end of the toddler range, but by 15 months many children do better with just one afternoon nap. If your child is getting significantly less than 11 hours total or fighting sleep at every turn, that’s a signal to look at the overall schedule rather than assuming the disruption will pass on its own.
Separation Anxiety and Bedtime Resistance
Separation anxiety at this age is genuinely different from what you may have seen at 8 or 9 months. Toddlers are more aware of the world now, more mobile, and more conscious of what it means when you walk out of the room. The protests tend to be louder, more physical, and harder to redirect. Separations are especially difficult when toddlers are tired or hungry, which is exactly the state they’re in at bedtime.
This doesn’t mean something is wrong. It’s a normal developmental spike that reflects your child’s growing attachment and awareness. Keeping bedtime routines predictable and brief helps. A consistent sequence of events (pajamas, book, song, lights out) gives your toddler a sense of what’s coming next, which reduces the anxiety of the transition to sleep.
Teething Pain at Night
First molars are the largest teeth to erupt so far in your toddler’s life, and the discomfort can be more intense than what earlier teeth caused. Because pain perception increases when there’s less distraction, teething often feels worse at night. If your child is drooling more than usual, chewing on things, or irritable during the day, molars may be contributing to the sleep disruption. The teething component is temporary, but it can overlap with the other 15-month changes and make the whole stretch feel longer than it is.
How Long It Lasts
Most toddler sleep regressions resolve within one to two weeks, provided you maintain consistent sleep habits throughout. The temptation is to introduce new sleep crutches during the rough patch: bringing your toddler into your bed, rocking them fully to sleep when they’d been falling asleep independently, or pushing bedtime much later. These adjustments are understandable in the moment but can extend the regression by creating new habits that are harder to undo.
If sleep disruptions persist beyond two to three weeks, the issue is more likely structural. That usually means the nap transition isn’t complete, the schedule needs adjusting, or an underlying issue like ongoing teething or illness is still in play. Growth spurts can also briefly increase sleep needs or cause overnight hunger, adding another variable to the mix.
What Actually Helps
The most effective response is adjusting the schedule while keeping everything else stable. If your child is still on two naps, try shifting to one nap around midday, aiming for that 1 to 2 hour window. Expect a few cranky late afternoons during the transition. You may need to move bedtime slightly earlier (by 30 minutes or so) to compensate for the lost nap while your toddler adjusts.
For separation anxiety at bedtime, keep your goodbye calm and confident. Lingering in the room or repeatedly coming back can reinforce the idea that bedtime is something to protest. A short, warm, and predictable routine works better than a long, drawn-out one. For teething discomfort, cold teething toys before bed and age-appropriate pain relief can take the edge off enough for your child to settle.
The 15-month regression feels disorienting because your toddler may have been sleeping well for months. But it’s driven by real, identifiable changes, and most families are through it within a couple of weeks.