Abstract Objective: The objective was to evaluate a 3‐year nationwide mass media campaign aimed at preventing weight gain. The campaign was aimed primarily at raising awareness of the importance of weight‐gain prevention and bringing these issues to the attention of the Dutch public. Research Methods and Procedures: Eleven serial, independent, cross‐sectional, population‐based telephone surveys were used to assess campaign awareness and impact ( N ranged between 483 and 493 for each of the 11 surveys). The surveys were conducted before and after six campaign waves. Multiple linear and logistic regression analyses were used to test for trends over time and for differences among the surveys for campaign awareness, message recall, perceived body weight status, overweight‐related risk perceptions, attitudes, perceived social support, self‐efficacy expectations, and motivations for preventing weight gain. Results: Campaign awareness ranged from 61% after the 1st campaign wave to 88.4% after the final wave. The campaign's television broadcasting activities were an important source of campaign awareness, from both the campaign's television commercials and television‐based free publicity. Message recall ranged from 41.9% to 68.1%. Small positive differences were found in attitudes, perceived social support, and intentions for preventing weight gain. Additionally, the results suggest mixed effects on self‐efficacy expectations and a negative effect on risk perception. Discussion: The campaign resulted in high campaign awareness, especially as a result of television commercials and free publicity on television. The results suggest that the campaign was able to create more positive attitudes and motivation but lower risk perceptions and efficacy for preventing weight gain.