Since its discovery as the 6th plant hormone in 1970, Brassinosteroids (BR) has been use with several purposes including: stress tolerance, photosynthetic enhancement and yield improvements. This work shows the results of exogenous foliar spraying of BioUltra (BR´s) in specific phenological stages of Valencia sweet orange to promote higher fruit set. Citrus trees were applied twice (during flower anthesis and pistil-fall) with a 0.02 and 0.04 ppm BR solution. All the applications were made using an organosilicon (0.2 ml l-1) as coadyuvant, and the controls were applied using water with the coadyuvant. Fruit set was determined by counting tagged flowers and, at the end of physiological fruit drop, the fruit were count. Results show a significant increase (73%) of fruit set obtain in the 0.04 ppm BRs treatment and a clear response to the increase in BRs concentration is evidenced. Future work will explore the effect of BRs on the photosynthetic rates using gas exchange approach.