Nationwide health promotion campaigns are an important part of government-funded health promotion efforts. Valid evaluation is important, but difficult because gold standard research designs are not applicable and the allocation of budget and time for evaluation is often very tight. In the Netherlands, Health Promotion Institutes (HPIs) are responsible for these campaigns. We conducted an exploratory study among the HPIs to gain better insight into goals, practices, conditions and perceived barriers regarding evaluation of these campaigns. Data were obtained through personal interviews with representatives of HPIs who had direct management responsibility for the evaluation of their campaigns. The HPIs typically made use of a pre-test–post-test design with single measurements before and after the campaign without a control group. In campaign preparations, HPIs used qualitative research to pre- and pilot-test some campaign materials, but true formative evaluation was rare. Besides, accountability to their sponsors, peers and the population at large, the most important reason to evaluate was to learn for future campaigns. In terms of the RE-AIM framework, evaluation was mostly restricted to Reach and Effects; hardly any evaluation of adoption, implementation or maintenance was reported. Budget and time constraints were reported as the main barriers for more extensive formative and effect evaluation. Evaluation of nationwide campaigns is standard procedure, but the applied research designs are weak, due to lack of time, budget and research methodology expertise. Next to additional budget and a longer-term planning, input from external experts regarding evaluation research designs are needed for evaluation improvement.