Tan spot caused by Pyrenophora triticirepentis is the main foliar diseases of wheat in Brazil. The effect of silicon (Si) on the components of resistance of a susceptible (Fundacep Horizonte) and a moderately resistant (Quartzo) wheat cultivar was studied in a controlled environment. Silicon was supplied as calcium silicate in the soil 30 days before sowing. At the booting stage, a conidial suspension of the fungus was sprayed onto the flag leaves of potted plants, which were incubated under moist conditions for 48 h. Afterwards, inoculated leaves were assessed for: incubation period (IP), infection efficiency (IE), area under lesion size curve (AULSC), lesion size (LS), severity (SEV) and area under severity curve (AUSC). Foliar Si concentrations were quantified at the end of the evaluations. Si supply to plants increased leaf Si concentration in 233% for Fundacep Horizonte (from 4.8 to 16.0 g kg−1 of dry matter) and 211% for Quartzo (from 5.3 to 16.5 g kg−1 of dry matter). In the Si + treatments, IP was longer by 24 and 17 h, IE declined by 53.5 and 65.5%, LS (at 264 h after inoculation) by 4.6 mm(from 9.5 to 4.9 mm) and 5.9 mm (from 8.2 to 2.3 mm), and SEV by 53% (from 54.4 to 18.8%) and 88% (from 47.7 to 5.5%) respectively, for the Fundacep Horizonte and Quartzo cultivars. The Si x cultivar interaction was not significant for AULSC and AUSC, and these variables were reduced by 55.8 and 80.8%, respectively, in plants supplied with Si. In conclusion, Si enhanced the resistance of wheat plants to tan spot development by affecting several resistance components, regardless of the resistance level of the cultivar. However, the greatest reduction in tan spot development by Si supply was observed when using a moderately resistant cultivar.