This study examined how employee participation and perceptions of line managers' support during a participatory organizational intervention were related to well-being over time. Although previous studies suggest that employees' and managers' active involvement in participatory organizational interventions may be related to well-being, little is known about the temporal aspects, such as at which time during the intervention these factors matter, or possible reciprocal effects. Building on conservation of resources theory, we tested hypotheses concerning direct, reversed, and reciprocal relationships between employee participation and perceptions of line manager support in relation to well-being. We used a four-wave panel design consisting of 159 hospital workers. Cross-lagged analyses showed that perceived line managers' support in the initiation and active phase was related to participation in the active phase. Participation in the initiation and active phase was related to well-being in the active and sustained phase, respectively. Results also revealed that participation in the initiation phase was related to perceived line managers' support in the active phase, which in turn predicted participation in the active phase, which translated into job satisfaction in the sustained phase supporting reversed and reciprocal effects in the form of resource caravans. Theoretical implications for research and practice are discussed.