Ricinoleic acid is obtained from castor bean and studies related to its effects on glucose and insulin dynamic are scarce in the literature. Eight male Crioulo breed horses (362 ± 16 of live weight, mean ± SD) were used in a replicated 4 × 4 Latin square design experiment that consisted of 10 days of adaptation and 7 days for data collection. The horses were allocated in each square to receive one of the following treatments: Control (0) and 1, 2, 3 and 4 g/d of ricinoleic acid (diet DM basis). Diets were composed of a commercial concentrate and Coast cross hay. Treatments did not affect DM and nutrient intake. Ricinoleic acid did not alter the nutrient digestibility, regardless of the dosage used. The quadratic effect was observed for glucose and insulin area under the curve. Ricinoleic acid quadratically affected glucose and insulin concentrations. Increasing dietary doses of ricinoleic acid altered glycemic and insulinemic responses of horses, and the present study recommends the dietary inclusion of 1.8 g of ricinoleic acid to improve horse's energetic metabolism.