Brassinosteroids (BRs) are a class of polyhydroxysteroids that have been recognized as a "sixth class of plant hormones". At present, 70 analogs have been identified, and among these, 24-epibrassinolide (24-eBL) is known to have an economic impact on plant metabolism, growth and productivity, and experience high stability under field conditions. Exogenous application of BRs are reported to confer resistance to plants against various abiotic stresses like heat, drought, heavy metals, salt and biotic stress like fungi and even viruses. Apart from resistance to biotic stresses, BRs also affect a broad spectrum of physiological responses like cell expansion, vascular differentiation, reproductive development, seed germination, flowering, fruit set and synthesis of antioxidant compounds in plants. In this study, the aim was to determine the best pre-harvest 24-eBL application for the accumulation of antioxidant compounds in 'Alphonse Lavallee' grape cultivar by using fuzzy logic modelling (FLM). For this aim, 24-eBL was applied to 9 years-old vines with 13 combinations including different application times that are our first input variables and 4 different concentrations (0.2, 0.4, 0.6 and 0.8 ppm) which are second input variables of our fuzzy logic model and control. Total phenolic content, total anthocyanin, trans-resveratrol, beta-carotene and ascorbic acid were examined as antioxidant compounds in grapes. One, some or all of these can be used as output variables of our FLM to get the optimum result. By making the data continuous the model can be used for obtaining useful information about untested data so that the best solution, that is the best 24-eBL concentrations and application times, can be attained at some non-measured input variables for each antioxidant compound.