Besides, reports of good crop from growing regions also weighed on prices.
At the National Commodity and Derivative Exchange, mustard seed for delivery in January contracts fell Rs 45, or 1.16 per cent, to Rs 3,850 per quintal, clocking an open interest of 2,260 lots.
Also, the delivery for April contracts drifted Rs 10, or 0.24 per cent, lower to Rs 4,108 per quintal with an open interest of 39,470 lots.
Marketmen said reducing of positions by participants, triggered by a weak trend in the spot markets, led to the fall in mustard seed prices at futures trade here.