A mixed methods study was used to transcend the traditional pre-, post-test approach of citizen science evaluative research by integrating adults’ test scores with their perceptions. We assessed how contributory entomology citizen science affects participants’ science self-efficacy, self-efficacy for environmental action, nature relatedness and attitude towards insects. Pre- and post-test score analyses from citizen scientists (n = 28) and a control group (n = 72) were coupled with interviews (n = 11) about science experiences and entomological interactions during participation. Considering quantitative data alone, no statistically significant changes were evident in adults following participation in citizen science when compared to the control group. Citizen scientists’ pre-test scores were significantly higher than the control group for self-efficacy for environmental action, nature relatedness and attitude towards insects. Interview data reveal a notable discrepancy between measured and perceived changes. In general, citizen scientists had an existing, long-term affinity for the natural world and perceived increases in their science self-efficacy, self-efficacy for environmental action, nature relatedness and attitude towards insects. Perceived influences may act independently of test scores. Scale instruments may not show impacts with variances in individual’s prior knowledge and experiences. The value of mixed methods on citizen science program evaluation is discussed.