Introduction: Tithonia diversifolia, also known as Mexican sunflower, is a tropical shrub with high forage potential, but limited information exists on the optimal harvest stage to balance yield and nutritional value. Methods: A 3 × 3 factorial design was implemented under tropical dry forest conditions in northern Peru, combining three regrowth stages (30, 45, and 60 days) with three plant fractions (leaf, stem, and leaf–stem mixture), with four replicates per treatment. Agronomic traits, dry matter yield, proximate composition, and in vitro dry matter digestibility (IVDMD) were evaluated. Results: Biomass yield increased significantly with harvest age, reaching 11.93 kg fresh weight and 3.45 kg dry matter per plant at 60 days, although with reduced nutritional quality due to a higher stem proportion. Leaves harvested at 30 days had the highest crude protein (16.5%) and soluble carbo...