Recent interest in the valuation of ecosystem services has provided tools for assessing the costs of invasive species in natural areas. This study evaluates the economic impacts of tamarisk (Tamarix sp.), an invasive woody shrub, on societally-valued ecosystem services in its naturalized range. Tamarisk, intentionally introduced from Eurasia, has invaded most riparian areas of the arid and semiarid western United States. In its naturalized range, tamarisk consumes more water than native vegetation, with significant economic implications in a region marked by water scarcity. Tamarisk also increases sedimentation in river channels, leading to increased frequency and severity of flood damage. Conservative economic estimates of these impacts indicate that the annual costs of tamarisk to the western United States total USD 280–450 ha⁻¹. Eradicating the invader and restoring native riparian communities throughout the region would cost approximately USD 7400 ha⁻¹. Full recovery of these costs, even with a highly conservative benefits estimate, would occur in as few as 17 years, after which the societal, ecological, and economic benefits of restoration would continue to accrue indefinitely.