At 15 months, waking up crying is extremely common and almost always tied to a combination of developmental changes happening at once. Your toddler’s brain and body are going through a massive growth period, and the most likely culprits are separation anxiety, teething pain from incoming molars, new motor skills like walking, and a possible nap transition. The good news: this phase typically lasts two to six weeks.
Separation Anxiety Peaks Around This Age
Between 6 months and 2 years, separation anxiety is at its strongest. At 15 months, your toddler has a much better grasp of object permanence, meaning they know you exist even when they can’t see you. That sounds like progress, and it is, but it also means they now realize you’re not there when they wake up in the dark. The result is crying at bedtime, crying when placed in the crib, and crying in the middle of the night when they wake between sleep cycles and find themselves alone.
This is especially intense right now because your toddler is also becoming more independent during the day. They’re imitating your actions, trying to do things on their own, and exploring constantly. Paradoxically, that growing independence creates a stronger need for reassurance that you’re nearby. The daytime confidence doesn’t carry over to 2 a.m.
First Molars May Be Breaking Through
The first molars typically erupt between 13 and 19 months, placing 15 months right in the thick of it. Unlike the front teeth, molars are large, flat, and have to push through a wide area of gum tissue. This makes them significantly more painful. Your toddler may not cry much during the day because they’re distracted, but at night there’s nothing competing with the discomfort.
Signs that teething is contributing to the night waking include increased drooling, chewing on everything, swollen or red gums toward the back of the mouth, and general fussiness that seems worse in the evening. If you suspect molars, a chilled teething ring before bed and age-appropriate pain relief can help take the edge off overnight.
New Physical Skills Disrupt Sleep
Around 14 to 15 months, most toddlers are taking their first steps, walking independently, or starting to climb furniture and stairs. The brain doesn’t stop processing these new skills at bedtime. Your toddler may wake up and immediately pull to standing in the crib, then cry because they’re stuck, overstimulated, or simply can’t settle back down. Some toddlers literally practice walking or climbing during the night without fully waking, then get upset when they find themselves in an awkward position.
A language explosion is also happening at this age. If your toddler is calling out new words in the middle of the night, their brain is in overdrive, processing the flood of new communication skills. This cognitive activity can fragment sleep and cause partial wakings that turn into full-blown crying episodes.
The Nap Transition Makes Everything Harder
Many toddlers begin dropping from two naps to one somewhere between 13 and 18 months. This transition rarely happens cleanly. For weeks, your toddler might need two naps some days and only one on others. Signs the transition is underway include refusing or protesting naps, taking very short naps, needing a late bedtime to fit both naps in, and (notably) frequent night wakings or early morning wakings.
The tricky part is that an undertired toddler who skips a nap and an overtired toddler who didn’t nap enough can both end up waking and crying at night. Overtiredness is especially problematic because it triggers a stress response that actually makes it harder to stay asleep. If your toddler recently dropped a nap or is fighting one of their two naps, this transition is likely contributing to the nighttime crying.
Night Terrors vs. Nightmares
If the crying episodes look intense, with screaming, thrashing, or wide-open eyes that don’t seem to register your presence, your toddler may be experiencing night terrors rather than simply waking up upset. During a night terror, your child appears frightened but cannot be awakened or comforted. Their eyes may be open, but they don’t recognize you. These episodes last 10 to 30 minutes, and your toddler typically has no memory of them the next morning.
Nightmares are different. Your toddler fully wakes up, recognizes you, and wants comfort. At this age, nightmares often involve themes of separation from parents, which ties back to the separation anxiety that’s peaking right now. If your toddler wakes crying but calms down when you hold them, that’s more consistent with a nightmare or a simple anxiety-driven waking than a night terror.
When Pain or Illness Is the Cause
Ear infections are worth considering if the crying is sudden, intense, and different from your toddler’s usual fussiness. Lying flat increases pressure on an infected middle ear, which is why ear pain often seems worse at night. Watch for tugging or pulling at the ears, fever, fluid draining from the ear, balance problems, or trouble responding to quiet sounds. If you see several of these signs together, an ear infection is a real possibility.
Other illness-related causes include throat pain, stomach discomfort, or a low-grade fever from any common virus. A toddler who was sleeping well and suddenly starts waking with inconsolable crying, especially with other symptoms, is worth evaluating for something beyond normal developmental disruption.
How to Respond to Nighttime Crying
A consistent, calming bedtime routine is the single most effective tool during this phase. A bath, a few books, a quiet conversation about the day, and soothing music all signal to your toddler’s brain that sleep is coming. Keep the routine the same every night and aim for the same bedtime. Predictability reduces anxiety.
When your toddler wakes crying at night, try giving them a moment to see if they can resettle on their own. Many 15-month-olds cry briefly between sleep cycles and fall back asleep within a few minutes. If the crying escalates, go in and offer brief, calm reassurance: a light pat, a quiet voice, but keep the interaction short and boring. The goal is to communicate that you’re there without creating a new sleep association that requires your presence every time they wake.
If you find yourself needing to stay in the room, you can try sitting near the crib and offering calm comfort until your toddler falls asleep, then gradually moving your chair farther from the crib over the course of several weeks until you’re outside the room. This approach works well for toddlers whose separation anxiety is the primary driver.
Whichever approach you take, expect the crying to temporarily get worse before it improves. Toddlers test new boundaries with impressive persistence. Consistency is what gets you through the regression. Changing strategies every few nights resets the process and can prolong it.
How Much Sleep Your 15-Month-Old Needs
Toddlers between 1 and 2 years old need 11 to 14 hours of total sleep per 24-hour period, including naps. If your toddler is getting significantly less than this, the night waking may be partly driven by a schedule that needs adjusting. Too little daytime sleep creates overtiredness, and too much daytime sleep can reduce nighttime sleep pressure. During the nap transition, tracking total sleep across the full day gives you a clearer picture than focusing on nighttime alone.