Play is central to children's learning and development in the early years, including the learning of mathematics. The aim of the present study was to explore how play skills are related to mathematical skills in toddlers by examining the correlations between different kinds of play skills and mathematical skills, and how level of play skills is related to mathematical skills. The participants were 1088 toddlers in Norwegian Early Childhood and Care institutions who were observed by the staff in 3-month periods beginning when they were 2½ years old. The skills in mathematics and play were assessed by structured observation. The overall scores for play skills and the scores for all types of play skills correlated significantly with the scores for all mathematical areas and the total score for mathematics. The skills "Interaction in Play" and "Independence in Play" displayed the strongest correlations with mathematical skills. "Rule-based Play" was difficult for the toddlers, whereas "Pretend Play" and "Exploring and Construction Play" correlated with mathematical skills and may be types of play that are more suitable when introducing mathematics in toddler groups. When the group of toddlers was divided into three subgroups according to their level of play skills, the level of play skills was strongly related to the level of mathematical skills. Toddlers with weak, middle or strong play skills also exhibited corresponding low, medium or high levels of mathematics skills, which emphasises the importance of understanding the relations between play and mathematical learning when working with toddlers.