OBJECTIVE: We assessed the association between fiber intake and fruit/vegetable consumption with the likelihood of weight gain in the previous 5 y in a Mediterranean population. METHODS: We conducted a cross-sectional analysis of participants (5094 men and 6613 women) in a multipurpose prospective cohort (Seguimiento Universidad de Navarra Study). Diet was measured by using a semiquantitative food-frequency questionnaire that was previously validated in Spain. We calculated the odds ratios of weight gain in the previous 5 y according to quintiles of energy-adjusted fiber intake and quintiles of energy-adjusted of fruit/vegetable consumption. We also considered the joint exposure to fiber intake and fruit/vegetable consumption. RESULTS: Multivariate-adjusted odds ratios for weight gain across quintiles 1 to 5 of fiber intake were 1.00 (reference), 0.86, 0.86, 0.70, and 0.52 (P for trend < 0.001) among men and 1.00 (reference), 0.99, 1.08, 1.05, and 0.72 (P for trend = 0.005) among women. We also observed a significant inverse association between total fruit/vegetable consumption and weight gain, but only among men (adjusted odds ratios, 0.78, 0.89, 0.70, and 0.54 for quintiles 2 to 5, P for trend < 0.001). The inverse association between fruit/vegetable consumption and weight gain in the previous 5 y was more evident among those with a high intake of total fiber, and the benefit of total fiber was more evident among those with a high consumption of fruits and vegetables. CONCLUSIONS: This study provides additional support to the inverse association between fiber or fruit/vegetable consumption and weight gain, thus emphasizing the importance of replacing some dietary compounds by such foods and fiber-rich products, which may help to avoid weight gain.