Mercury is a ubiquitous environmental contaminant and potent neurotoxin. In aquatic environments, mercury can be transformed into methylmercury (MeHg), which bioaccumulates in aquatic food webs, including fish. MeHg has been shown to transfer from female fish to developing eggs; however, relatively little is known regarding effects of maternally-transferred MeHg on fish embryos. Here, we evaluate the effects of maternally-transferred MeHg on fathead minnow (Pimephales promelas) embryos. Embryos were collected from adult fatheads exposed for 30 days to one of three diets spiked with MeHg: a control diet (0.02 ppm Hg dry weight), a low diet (0.87 ppm Hg dry weight), or a high diet (5.5 ppm Hg dry weight). No effects on spawning frequency, clutch size, or total egg output were observed. In embryos, Hg concentration was a function of female diet and the duration (number of days) of female exposure. Compared to controls, embryos from the low diet treatment displayed altered embryonic movement patterns (hyperactivity), as well as decreased time to hatch. Embryos from the high diet treatment had delayed hatching and increased mortality compared to the other treatments. Collectively, these results suggest maternally transferred mercury may impact survival, behavior, and developmental milestones of embryo-larval stages of fish.