Piperonyl butoxide (PBO) is a common insecticide synergist used in agricultural products throughout the U.S. PBO increases the effectiveness of insecticides by blocking insect detoxification mechanisms. On its own, PBO is considered relatively non-toxic to non-target organisms such as honey bees. However, little research has evaluated its toxicity and sublethal effects on other bees, such as the common eastern bumble bee (Bombus impatiens). Using Environmental Protection Agency (EPA) guidelines, we calculated a field-realistic concentration of PBO and dosed bumble bee microcolonies. Mortality, sucrose consumption, and the total number of brood cells and nectar cups were compared between control and PBO-dosed microcolonies. In general, we found limited effects of PBO on any bumble bee response variable. Future studies should evaluate a larger range of field-realistic doses on bees in addition to measuring other sublethal effects such as behavior and physiology.