With the rising popularity of citizen science, there’s a growing focus on effective assessment methods for participant outcomes. Unlike many biodiversity programs, which typically emphasize programmatic outcomes, this study examined how Blue Thumb, an Oklahoma water quality citizen science program, influences volunteer behaviors, interests, and motivations using an explanatory survey based on Phillips et al.’s (2018) evaluation framework. Although there were no significant differences in behaviors and interests between new and experienced volunteers (N = 74), motivations varied significantly, distinguishing between intrinsic and extrinsic reasoning. Blue Thumb volunteers already displayed pro-environmentalism and strong scientific interests before joining, and these traits persisted rather than being cultivated through participation. The study’s insights informed Blue Thumb’s future volunteer recruiting and retention strategies. While contributing to research utilizing a common framework, future studies should incorporate qualitative methods to provide context for a deeper understanding of the quantitative findings.