We conducted and evaluated a low-dose copper treatment (applied as EarthTec QZ) to suppress zebra mussel (Dreissena polymorpha) veliger abundance and settlement in a 66.3 ha bay in Lake Minnetonka (Hennepin County, MN) over a 3-y period. We maintained a mean (standard deviation [SD]) concentration of 83.0 (10.3) µg/L as copper over the 10-d treatment period, much lower than the maximum allowable 1 mg/L as copper. Veliger density was reduced from 6.0 veligers/L before treatment to 0.3 veligers/L following the treatment period. Posttreatment zebra mussel settlement was 1900 times lower in the treated bay compared to an untreated bay days after the treatment despite similar pretreatment veliger densities. Veliger density and settlement remained suppressed nearly 2 y following the treatment. Sampling for adult zebra mussels within the treated bay returned variable results but survival of caged adult zebra mussels indicated ~30% treatment-related mortality. Copper in surface waters returned to near pretreatment concentrations 90 d after treatment. Our study demonstrates that low-dose applications of a copper molluscicide can effectively reduce zebra mussel veliger densities and settlement. Additionally, Our study evaluated nontarget effects before and after treatment. Chlorophyll-a concentration increased in both the treated and reference bays 1 and 14 d posttreatment. Although zooplankton community composition changes occurred in both bays over the course of this study, zooplankton abundance and diversity initially decreased in the treated bay but gradually recovered and one year later was back to pretreatment and reference bay levels. We observed no significant differences in benthic invertebrate abundance or diversity between the treated and reference bays. Among caged organisms, copper bioaccumulation was higher in both mussel species than in fish, and among fish, was highest in fathead minnow. These findings contribute to our understanding of the potential impacts of copper-based pesticides on aquatic ecosystems and provide insights for zebra mussel management.