To promote sun safety by implementing different plans for sunscreen use, different psychological interventions are compared. Self-regulatory strategies such as action planning and coping planning are seen as proximal predictors of actual behavior. The study compares a pure planning intervention with a broader resource communication and examines differential effects at different stages of change. A sun safety online study was designed with two intervention groups (resource communication versus planning) and one control group at two assessment points, 2 weeks apart. Participants (N = 292) were grouped post hoc according to their stage of change, resulting in 51 pre-intenders (no intention to use sunscreen), 102 intenders (high intention but no regular use of sunscreen) and 139 actors (sunscreen use on a regular basis). No overall treatment effects on planning, but an interaction between time, stage and intervention emerged. The resource communication was more effective for pre-intenders, whereas the planning intervention proved more effective for intenders. A planning treatment was more beneficial in motivated individuals, whereas a broader approach was better for unmotivated ones. Findings highlight the potential that stage-matched interventions might have in the context of sun safety promotion.