Citizen science approaches to data collection are growing in popularity, in part because of their potential for achieving both scientific and educational objectives. Evaluating the impacts of participation on citizen scientists is important, yet such evaluations are still relatively rare. In addition, recent literature reviews indicate that existing studies often focus on content learning, make limited use of existing scales, and rarely report null results. This paper reports an evaluation of the demographic profile, motivations and learning outcomes of participants in the Dutch National Bee Survey, a national-scale citizen science project involving citizens in collecting observational data of wild bees. Using a repeated measures survey study, we assessed the impact of participation on respondents’ attitudes and behavioural intentions regarding bees, and their attitudes towards nature, citizenship, and citizen science. Our baseline (N = 373) and follow-up (N = 208) surveys indicate that our respondents are of a relatively high age and education level, have a pre-existing affinity with nature, and are strongly motivated by conservation concerns and learning about bees. Assessment of learning outcomes indicated a significant difference between two types of self-report questions: respondents reported significant gains in knowledge and appreciation of wild bees, yet attitudinal scales indicated no significant shifts in attitudes towards bees, nature, citizen science, or citizenship. In our discussion, we suggest several explanations for this finding, including respondents’ pre-existing affinity with nature, and advance suggestions for future research into citizen science learning outcomes.