<p>Healthier diets are associated with fewer mental health symptoms, whereas higher consumption of ultra-processed foods is associated with psychological distress. This pilot study aimed to evaluate the impact of a nutrition education program, using validated measures of dietary intake (ASA24) and mental wellness (Warwick–Edinburgh Scale) before and after the intervention. A longitudinal interventional study was conducted in university students for 3 months, with seminars, healthy snack breaks, a book and cooking techniques class. At baseline, students reported consuming fruit and calcium below the recommendations, while ultra-processed food, saturated fat, and sodium intake were over the limits. Initially, mental wellness was inversely related to sodium. Following the intervention, fruit and calcium intakes increased, whereas sodium and ultra-processed food consumption decreased significantly (<i>p</i> &lt; 0.05). Mental well-being showed positive trends, meanwhile its association with sodium consumption weakened over time (Initial: Pearson&#xa0;=&#xa0;-0.73, r² = 0.54, <i>p</i> &lt; 0.001 vs. Final: Pearson = 0.24, r² = 0.05, <i>p</i> &gt; 0.05), suggesting a potential attenuation of unhealthy diet and mental wellness associations following the intervention. The program produced targeted improvements in diet quality, but multi-level strategies are likely required to achieve overall dietary adequacy. Mental well-being improved directionally without significant change, supporting nutrition education as a contributory component of well-being rather than a stand-alone solution.</p>