Background/Objectives: Professional mixed martial arts (MMA) athletes routinely partake in practices to elicit rapid weight loss before official weigh-in, followed by aggressive rehydration and nutritional recovery before competition. Although weight-cutting strategies have been widely described, there is limited information characterizing nutrient intake, food group selection, and fluid consumption during the pre-weigh-in, post-weigh-in, and fight-day periods. This cross-sectional study examined self-reported dietary intake of professional MMA fighters during the 24 h before weigh-in, post-weigh-in, and on fight day. Methods: Participants self-reported all foods and beverages consumed during three distinct competition phases: pre-weigh-in, post-weigh-in, and fight day. Changes in energy, macronutrient, fiber, sodium, and fluid intake across competition phases were evaluated using linear mixed-effects models. Results: The pre-weigh-in period was characterized by severe carbohydrate and fiber restriction with reduced fluid intake, whereas post-weigh-in intake shifted toward aggressive carbohydrate, fluid, and sodium replenishment alongside reduced fat consumption. Food group analysis demonstrated systematic elimination of vegetables, dairy products, legumes, whole grains, fried foods, and other high-fiber foods before weigh-in, with continued restriction of high-fat and high-fiber foods throughout the recovery period. Conclusions: These findings provide a comprehensive characterization of nutrient intake, food selection, and fluid consumption across the final stages of professional MMA competition preparation.