BACKGROUND Many school‐based recess interventions have been shown to be effective in increasing physical activity but their relative efficiency compared to other school‐based programs are unknown. This study examined the cost‐effectiveness of Ready for Recess, a program designed to increase students' physical activity in 2 elementary schools. METHODS Standard cost‐effectiveness analysis method was used from a program's perspective for this study. Program effectiveness was measured as total metabolic equivalent (MET) hours gained. Program costs included equipment, training, and personnel costs during the 1‐year intervention. The cost‐effectiveness was measured as the ratio of program costs to total MET‐hours gained. RESULTS Ready for Recess cost $27,643.97 for the 2 schools in the first year of implementation. Physical activity increased by 1.8 MET‐hours per day per student. Approximately 32 cents were spent on Ready for Recess to produce an additional MET‐hour per student per school day in the 2008‐2009 school year. CONCLUSIONS Ready for Recess was cost‐effective in its first year of implementation using 35 cents as a benchmark and it was cost‐effective relative to other school‐based physical activity interventions. The program may be more cost‐effective if implemented for a longer time and on a larger scale.