There’s no “perfect” age for sleep training, says Dumaplin. “You can start to work on healthy sleep habits from birth, but for formal sleep training, we need to wait until babies are developmentally ready,” she says. “That can be as early as 5 months, and sleep training can be appropriate from 5 months until your little one reaches 5 years. The best age for sleep training is when parents decide it’s right for their family.”