Chemical control is the most used method for white mold (Sclerotinia sclerotiorum) management by farmers, but fungicide effectiveness can be hampered by the emergence of resistant S. sclerotiorum isolates. The objective of this work was to develop a method to screen S. sclerotiorum resistance to fungicides by employing 96-well microplates and Alamar Blue dye, used as a cell viability indicator. Experimental procedures involved 20 isolates of S. sclerotiorum from different Brazilian regions, tested at 1 × 10², 10³ and 10⁴ ascospores mL^-1, along with Carbendazim and Fluazinam fungicides at 10, 100 and 1000 ppm. Evaluations included incubation periods of 72, 96, 120 and 144 hours, and comparisons of isolate aggressiveness after inoculation of common bean plants. Resistance to Carbendazim was observed in 90% of isolates, compared to 55% of isolates resistant to Fluazinam. Isolates SS48 and SS67 showed multiple resistance to both fungicides (100ppm) and high aggressiveness. Resistance to fungicides was not associated to geographical origin of isolates, according to the hierarchical grouping test by level of resistance. Despite an average of 40 days necessary to obtain ascospores from carpogenic germination in the laboratory, the microtiter method consists in a fast procedure, with reduction of labor, bench area and toxic laboratory residues. This is a new method that allows laboratory routines for screening S. sclerotiorum resistance to fungicides from any host plant.