Field trials were conducted to evaluate the effect of different periods of weed interference on weed infestation, growth and yield of soybean in 2016–2017 cropping seasons. In both years, soybean grain yields ranged from 888–1148 kg ha ^-1 in plots where weeds were allowed to grow until harvest to 2103–2389 kg ha ^-1 in plots where weeds were controlled until harvest, indicating a 52–58% yield loss with uncontrolled weed growth. Weed interference until 3 weeks after sowing (WAS) had no detrimental effect on soybean growth and yield provided the weeds were subsequently removed. However, further delay in weed removal until 6 WAS or longer depressed soybean growth and resulted in irrevocable yield reduction, with the number of pods per plant being the most affected yield component. For optimum growth and yield, it was only necessary to keep the crop weed-free between 3 and 6 WAS.