Tithonia, commonly known as Mexican sunflower, is a shrub belonging to the Asteraceae family. It is widely distributed throughout the humid and sub humid tropics of Central and South America, Asia and Africa. Tithonia has been shown to be an excellent forage for ruminant nutrition, however few studies have been undertaken to evaluate yiel and nutrional quality for dairy cattle feeding. The objective of this study was to evaluate biomass production and nutritional quality of Tithonia diversifolia harvested at 3 different ages and fertilized with 3 N doses. The experiment was carried out in the province of Guanacaste, Costa Rica. A randomized block experimental design was used in a split plot arrangement with 4 replications. N rates (0, 150, and 300 kg/ha/yr) were allocated to the main plots, and harvest times (45, 60 and 75 d of regrowth) were allocated to the subplots. DM yield was affected (P < 0.05) by the different variables. Plants receiving 300 kg of N and harvested at 75 d of age, yielded 12.1 tons of DM/ha/yr, while plants receiving 0 kg of N and harvested at 45 d of age produced 4.8 tons of DM/ha/yr. CP concentration was affected by treatments (P < 0.05) and values ranged between 10.4 and 25.7%. CP yield was affected (P < 0.05) by N rate and harvesting age. Plants fertilized with 300 kg of N and harvested at 75 d of age produced 1.9 tons of CP/ha/yr. NDF and lignin concentration were highest (P < 0.05) when plants received 0 kg of N and were harvested at 75 d of age (57.9 and 19.2%, respectively). Ash content was also affected by treatments (P < 0.05) and values ranged from 9.8 to 17.5%. Results suggest that Tithonia diversifolia seens to be a promising forage for dairy cattle feeding in Costa Rica with best yields and nutritive quality when using N rates ranging from 150 to 300 kg/ha/yr and a harvesting age of 60 or 75 d.