Sleep disruptions at 15 months are extremely common and usually temporary, lasting one to two weeks. This age is a collision point for several big changes: your toddler’s brain is processing new motor skills like walking and climbing, separation anxiety is peaking, first molars may be pushing through, and nap needs are starting to shift. Any one of these can wreck sleep. At 15 months, they often hit at the same time.
The 15-Month Sleep Regression
Between 14 and 16 months, many toddlers who previously slept well suddenly start fighting bedtime, waking multiple times at night, or refusing naps. This is commonly called the 15-month sleep regression, and it’s driven by a surge of developmental activity. Your toddler’s brain is working overtime to process new physical skills (taking steps, climbing furniture, navigating stairs) and cognitive leaps (imitating your actions, understanding that you still exist when you leave the room). All of that mental work spills into sleep.
The good news: this regression typically resolves in one to two weeks without any major changes to your routine. The key is not to overhaul your approach in the middle of it. Introducing new sleep habits during a regression, like bringing your toddler into your bed or rocking them to sleep when you didn’t before, can create patterns that outlast the regression itself.
Separation Anxiety Peaks Around This Age
Many toddlers who sailed through infancy without much separation anxiety start showing it for the first time at 15 or 18 months. Your child now understands object permanence well enough to know you’re somewhere else when you leave the room, but not well enough to feel confident you’re coming back. That combination makes bedtime, when you literally walk away and close the door, genuinely stressful for them.
Separations are harder when kids are tired, hungry, or sick, which at this age is most of the time. A few things help. Keep your goodnight ritual short and consistent: the same steps in the same order every night. A quick, loving goodbye builds more security than a long, drawn-out one. If your toddler cries, lingering tends to extend the anxiety rather than soothe it. Over time, consistently leaving and consistently returning builds the trust that lets them relax at bedtime.
Practicing brief separations during the day can help too. Letting a grandparent or trusted friend watch your toddler for even an hour reinforces the idea that you leave and come back.
Teething Pain, Especially First Molars
Around 13 to 19 months, the first molars start coming in. These are the largest teeth to erupt so far, and the process is notably more uncomfortable than the front teeth were. In a clinical study of teething symptoms, 82% of children experienced sleep disturbances in the days leading up to a tooth breaking through. The disruption was worst in the four days before eruption, dropped significantly on the day the tooth appeared, and was largely gone within three days after.
That timeline matters because it tells you two things: teething-related sleep problems are real, and they’re short-lived per tooth. If your toddler is drooling heavily, chewing on everything, and more irritable than usual alongside the sleep issues, molars are a likely contributor. Extra comfort and cuddles during this window have been shown to help with both the pain and the sleep disruption. If your child seems to be in significant pain, talk to your pediatrician about appropriate pain relief.
The Two-to-One Nap Transition
Most toddlers drop from two naps to one somewhere between 14 and 18 months. This transition is messy, and it can look a lot like a sleep problem when it’s really a scheduling problem. Your toddler may not be tired enough for the morning nap anymore, but skipping it leaves them overtired by afternoon, which then disrupts nighttime sleep.
Signs your child is ready to drop to one nap:
- They seem content and happy when naptime approaches, rather than cranky
- They take much longer to fall asleep at one of their two naps
- They’re waking earlier in the morning despite going to bed easily and napping well during the day
If you’re seeing these signs, try gradually pushing the morning nap later by 15 to 30 minutes every few days until it merges into a single midday or early afternoon nap. The transition itself can take a few weeks, and you might have some rough days where your toddler is overtired. That’s normal. Once the single nap is established, nighttime sleep often improves.
How Much Sleep a 15-Month-Old Needs
Toddlers between 12 and 24 months need about 11 to 14 hours of total sleep per day, including naps. Most of that should come at night, with one to two hours during the day. If your toddler is getting significantly less than 11 hours total, the sleep disruptions you’re seeing may be compounded by a genuine sleep deficit, which paradoxically makes it harder for toddlers to fall and stay asleep. Overtired children produce more stress hormones, which keep them wired.
If your toddler is getting 12 or 13 hours total but distributing it differently than before (longer nap, shorter night, or vice versa), that’s less concerning. The total matters more than the exact breakdown.
Your Bedtime Routine Matters More Than You Think
A predictable bedtime routine is one of the most effective tools for reducing how long it takes a toddler to fall asleep. Researchers at the University of Pennsylvania found that parents who implemented a simple three-step routine (bath, massage, and quiet cuddling or singing) saw results within two weeks. Their children, aged 7 to 36 months, fell asleep faster and slept longer.
The specific steps matter less than the consistency. What you’re doing is giving your toddler’s brain a reliable sequence of cues that sleep is coming. Aim for 20 to 30 minutes, the same order every night, ending in the room where your child sleeps. Screens should be off well before the routine starts, since the blue-toned light from phones and tablets suppresses the hormones that make your toddler feel sleepy. If you use a nightlight, a warm-toned, dim light is ideal.
Signs Something Else Is Going On
Most 15-month sleep problems are developmental and resolve on their own. But a few patterns suggest something medical worth investigating.
Loud snoring, gasping, or snorting during sleep can be signs of obstructive sleep apnea. In young children, this is most commonly caused by enlarged tonsils or adenoids. Other clues include mouth breathing during sleep, restlessness, excessive daytime sleepiness or irritability, and hyperactivity. If your toddler snores most nights and seems unrested even after a full night of sleep, it’s worth raising with your pediatrician.
Ear infections are another common culprit at this age. Lying down increases pressure in the middle ear, which makes the pain worse. If your toddler was sleeping fine and suddenly wakes screaming, especially with a fever or after a cold, an ear infection is a strong possibility.
Frequent night waking that persists beyond three or four weeks, doesn’t respond to consistent routines, and isn’t tied to any obvious developmental change is also worth discussing with your child’s doctor. Most of the time, though, what you’re dealing with is a normal, exhausting, temporary phase.