The complementary activity of 4-hydroxphenylpyruvate dioxygenase (HPPD)-inhibitors and atrazine is well documented, but the use of atrazine is restricted in some geographical areas including the province of Quebec in Canada necessitating the evaluation of atrazine alternatives and their interactions with HPPD inhibitors. The objectives of this study were to determine if mixing HPPD-inhibitors with atrazine alternative photosystem II (PS II)-inhibitors, such as metribuzin and linuron applied PRE, or bromoxynil and bentazon applied POST, results in similar control of multiple-herbicide-resistant (MHR) waterhemp [Amaranthus tuberculatus (Moq.) Sauer] in corn. Ten field trials, five with herbicides applied PRE and five with herbicides applied POST, were conducted in Ontario, Canada in fields infested with MHR A. tuberculatus. Isoxaflutole, applied PRE, controlled MHR A. tuberculatus 58% to 76%; control increased 17% to 34% with the addition of atrazine, metribuzin, or linuron at three of five sites across 2, 4, 8, and 12 weeks after application (WAA). The interaction between isoxaflutole and PS II-inhibitors, applied PRE, was additive for MHR A. tuberculatus control, and biomass and density reduction. Mesotrione, tolpyralate, and topramezone, applied POST, controlled MHR A. tuberculatus 54% to 59%, 61%, and 44% to 45%, respectively, at two of five sites across 4, 8, and 12 WAA. The addition of atrazine, bromoxynil, or bentazon to mesotrione improved MHR A. tuberculatus control 29%, 34%, and 22%, to tolpyralate improved control 2%, 20%, and 10%, and to topramezone improved control 3%, 14%, and 8%, respectively. Interactions between HPPD- and PS II-inhibitors were mostly additive; however, synergistic responses were observed with mesotrione + bromoxynil or bentazon, and tolpyralate + bromoxynil. Mixing atrazine alternatives, metribuzin or linuron with isoxaflutole, applied PRE, and bromoxynil or bentazon with mesotrione or tolpyralate, applied POST, resulted in similar or better control of MHR A. tuberculatus in corn (Zea mays L.).