The purpose of this experiment was to determine the influence of the soil application of sulphur (S) on concentrations of micronutrients in the root residues, straw and oil cake of white and Indian mustard. The plant material for chemical analyses originated from a controlled field experiment conducted in experimental fields at the University of Warmia and Mazury in Olsztyn, Poland (2006–2008). In both white and Indian mustard, the richest source of Cu (7.2; 7.0 mg/kg dry matter (DM)) and Zn (64.6; 55.3 mg/kg DM) was the oil cake from mustard seeds. Regarding Mn, both white and Indian mustard accumulated the highest content of this element in roots (48.2; 50.8 mg/kg DM), less in oil cake (31.9; 35.5 mg/kg DM) and the least Mn was determined in straw of both species (24.0; 17.1 mg/kg DM). The application of sulphur caused a significant increase in the concentration of Zn and Mn in white mustard roots. The content of micronutrients in roots of Indian mustard was not differentiated significantly by S fertilization. The application of sulphur caused a significant decrease in the content of Mn in white mustard straw and Cu in Indian mustard straw. The content of micronutrients in white mustard oil cake and Indian mustard oil cake was not significantly changed by S fertilization.