Psychological detachment occurs in the absence of work ruminations during non-work time and is a vital component in the recovery from work-related fatigue, avoiding burnout, performance decrement and detrimental health-outcomes. Overcommitment to work entails excessive job involvement and resembles poor detachment. Detachment and overcommitment are influenced by characteristics of the worker, their work, and their leisure time, but few studies have examined the effects of work or leisure demands on detachment and overcommitment. The current study examined the activity demands, detachment and overcommitment ratings of 51 workers and university students by having participants complete nine internet-based surveys over four weeks, and analysing data with a multilevel modelling approach. Rates of psychological detachment were found to be increased by physically demanding leisure activities, and decreased by mentally demanding work activities when leisure activities were mentally undemanding. In addition, detachment rates were higher when work activities were emotionally demanding and leisure activities emotionally undemanding, and when work activities were emotionally undemanding and leisure activities emotionally demanding. Overcommitment was found to be increased by leisure activities which were mentally demanding or emotionally demanding. Work ruminations during leisure time were therefore found to be influenced by work and leisure demands, with the manipulation of leisure demands thereby offering a method through with to diminish or buffer the detrimental impact of arduous work demands on the recovery from fatigue.