In calves, play behavior is a promising indicator to assess both compromised and enhanced welfare. However, quantifying play is difficult due to its rare and irregular occurrence. We aimed to validate 1 Hz accelerometer recordings to measure locomotor play of dairy calves in their home-pens. Accelerometer data were combined into 10 s periods and periods were categorized as PLAY/NOPLAY using quadratic discriminant analysis. Comparing these periods with behavior recorded from video, play was correctly classified in 79% of cases. Based on a correlation of rP=0.87 with observed play intervals, it may be used as a proxy to replace behavior observations.