Objective: Firefighters’ eating habits may be an additional risk factor for metabolic diseases. We assessed eating habits of firefighters, compared them with national guidelines, and evaluated the impact of a prevention program. Methods: Twenty-eight professional firefighters from a Swiss airport benefited from a healthy-eating program. Food intake, eating behavior, and anthropometric data were collected at baseline and 1-year follow-up using an electronic food record, questionnaires, and bio-impedance. Results: Participants had unbalanced diets with low-quality food choices associated with low intakes of fibers and micronutrients compared with national guidelines. Intervention did not impact eating habits or anthropometrics data at the group level, but changes were measured in sub-groups. Main reported barriers for healthy eating were lack of motivation, prioritization, or time. Conclusions: Intensive and culturally tailored prevention interventions targeting nutritional behaviors are needed at the individual, group, and organizational levels.