Indian mustard (Brassica juncea L. Czern) cultivation is suggested for regions with short seasons and low rainfall. Although there have been many studies conducted on agronomic production of mustard in Iran, the information regarding the interactive impact of cropping seasons and nitrogen fertiliser on growth characteristics and yield quality of mustard plant is still insufficient and requires further investigation. This study focused on the possible implications of different cropping seasons and different nitrogen levels on selected agronomic traits in mustard. In this experiment, five different doses of nitrogen and two sowing periods were used to assess for their combined effects on the growth parameters, seed yield and agronomic characteristics of mustard in the semi-arid climatic conditions of Takestan. The results revealed that cultivation seasons and nitrogen rates had a significant effect on plant height, biomass yield, number of siliques per plant, seed oil content and seed yield.