Red spider mites, Oligonychus coffeae (NIENTER) and Oligonychus biharensis (HIRST) are important pests in mango cultivation of the Nansei Archipelago, southwestern Japan. We investigated the acaricidal effects of sulfur on the two mite species in the laboratory and field. In the laboratory corrected mortality of female adults was more than 85% in both mites and they died at 3 days after spraying with sulfur WP (wettable powder) or acequinocyl FL (flowable) used as a standard acaricide. Corrected mortalities of eggs treated with the sulfur agent were 0% in both mites, whereas those of hatchlings were more than 95%, indicating that the sulfur caused high mortalities to female adults and their hatchlings but not to the eggs. In a greenhouse, an application of sulfur WP was highly effective in suppressing the populations of the two mite species on mango trees. The two acaricides reduced the number of predatory mites of phytoseiidae on mango trees compared with the number on untreated control trees. More stains due to droplets of sprayed chemicals remained on the skin of harvested mango fruits when sulfur WP was sprayed just before bagging of the fruits than after bagging. We conclude that sulfur is highly effective in controlling spider mites on mango but its spraying should be avoided shortly before bagging for harvesting fruits without stains. We discussed the efficacy of sulfur acaricides in mango cultivation.