There is an increasing interest in outdoor play, both in research and in policy. However, in (re)designing, planning and managing the public space, there is still limited attention for children’s actual playing behavior. A lot of urban planning decisions are based on adults’ perceptions of children’s playing behavior and focus on formal play spaces, rather than on their actual behavior and on other, more informal, play places children might also use. Therefore, the purpose of this study was to explore where children play outdoors, with whom and what kind of activities they are performing there. Between February 2022 and March 2023 1,127 – mainly primary school - children were systematically observed after school in three post-war residential districts in three cities in The Netherlands. The majority of the children were between 5-8 years old (50%). Above the age of 8 years, substantially more boys (70%) than girls (30%) were playing outdoors. Most of the children (79%) were playing with other children, 8% were playing alone. The playground was the most popular play space (36% of the observed children were playing there), followed by public sports fields (14%) and sidewalks (13%). With respect to the type of activities, relaxing (21%) was the most common activity, followed by ball sports (14%), climbing or hanging (11%), swinging (10%), and riding on wheels (9%). This study showed differences in play behavior by gender, age, district and play space and stress the need for a broader definition of play, and for focusing on formal as well as informal play spaces.