We investigated nonindustrial private forest (NIPF) owners' invasive plant risk perceptions and mitigation practices using statistical analysis of mail survey data and qualitative analysis of interview data collected in Oregon's ponderosa pine zone. We found that 52% of the survey sample was aware of invasive plant species considered problematic by local natural resource professionals; 70% was concerned about these species; and 46% had treated invasive plants on their parcels. Owners' perceptions of invasive plant risks fell along a spectrum ranging from a lack of awareness or concern, to the view that invasive plant infestations have discrete causes and controllable consequences, to the perception that incursions by invasive plants have diffuse causes and uncontrollable effects. Being aware or concerned about invasive plant species were predictors (p ≤ 0.001) of whether owners treat their parcels to control invasive plants. Holding wildlife habitat and/or biodiversity as an important forest management goal was also a predictor (p ≤ 0.08) of whether owners treated their parcels to control invasive plants. Some owners were sensitive to the risks of invasive plant infestations from nearby properties, and a surprisingly high percentage of respondents had cooperated with others in forest management activities previously. Our findings suggest three approaches to increasing the frequency of invasive plant mitigation by NIPF owners that hold promise: (1) raising awareness and concern about invasive plants and their impacts on forest management goals that owners care about, such as wildlife habitat and/or biodiversity; (2) providing assistance to help owners mitigate invasive plants they feel unable to control; and (3) engaging owners in coordinated efforts across ownership boundaries to address invasive plant risks.