Abstract: An experiment was carried out in the Crop Botany Field Laboratory, Bangladesh Agricultural University, Mymensingh to find out the effect of indigenous mulches viz. rice straw, ash and sawdust on the microclimate, growth and yield of mustard crop cv. Shafol (Brassica campestris var. Yellow Sarson) during the winter season extended from November 2008 to February 2009. As compared to ash mulch and control (i.e. no mulch), the straw and sawdust mulches decreased the temperature but increased the moisture content of the soil. The mustard crop grown with sawdust mulch showed better performances for most of the parameters like shoot height, number of primary branches/plant, leaf area index, dry matter accumulation and yield components and yield. The sawdust mulched crop produced (1.54 t ha-1) about 35 and 20% higher seed yield than the crops grown with straw mulch (1.00 t ha-1) or no mulch (1.24 t ha-1). A heavy mulch cover like rice straw is unsuitable for mustard cultivation because the seedlings are so soft and succulent that many plantlets could not emerge out successfully by penetrating up through the straw mulch cover thus fail to establish as good crop stands. In contrast, the loose or powdery mulch like sawdust is proved to be beneficial for establishing good crop stands with higher production of mustard.