Only few studies so far have examined recovery from work during workday breaks. In this intervention study, based on the effort-recovery model and the conservation of resources theory, we examined how to enhance recovery during lunch breaks. More specifically, we examined the within-person effects of lunchtime park walks and relaxation exercises on employees’ levels of concentration, strain, and fatigue experienced at the end of a working day. We moreover tested whether detachment from work and enjoyment experienced during lunch breaks transmitted the effects of these activities to well-being outcomes. Participants in the park walk (n = 51) and relaxation (n = 46) groups were asked to complete a 15-min exercise during their lunch break on 10 consecutive working days. Afternoon well-being, lunchtime detachment, and lunchtime enjoyment were assessed twice a week before, during, and after the intervention, altogether for 5 weeks. Multilevel analysis results showed that park walks at lunchtime were related to better concentration and less fatigue in the afternoon through enjoyment. Relaxation exercises were related to better concentration in the afternoon via detachment. In addition, relaxation exercises were directly linked to lower levels of strain and fatigue in the afternoon. Our study suggests that on days on which employees engage in recovering activities during lunch breaks, they experience higher levels of well-being at the end of a working day. These results add to the theory-based knowledge on recovery during workday breaks and highlight the importance of breaks for organizational practices.