Seed shatter of wild oat (Avena fatua L.), green foxtail [Setaria viridis (L.) P. Beauv.], wild mustard (Sinapis arvensis L.), cleavers (Galium spurium L. and G. aparine L.), wild buckwheat (Polygonum convolvulus L.), and kochia [Kochia scoparia (L.) Schrad.] was evaluated in field pea, spring wheat, and canola fields in Saskatchewan in 2014 and 2015. Seed shatter was assessed using shatter trays collected once a week during the crop ripening stage, as well as at swathing or direct-harvest (direct-combining). Seed shatter differed among weed species in field pea and wheat at maturity: 22%–30% for wild oat, and generally ≤10% for the other species. Seed shatter of investigated weeds in canola at swathing, including that of wild oat, was uniformly low (<5%). The relatively low level of seed shatter for cleavers, wild mustard, green foxtail, and wild buckwheat suggests that these species may be suitable candidates for harvest weed seed control (HWSC). Because of the amount and timing of wild oat seed shatter, HWSC may not reduce population abundance of this grassy weed, except in canola when swathed.