<p>iNaturalist is a growing citizen science (CS) tool with great potential for biology education. Given the urgency of the biodiversity crisis, it is critical to raise awareness among preservice teachers (PT) as they impact future generations. Citizen Science has proven to be an effective educational tool. Activities with the iNaturalist application were conducted with preservice primary school teachers (PST) and biology teachers (BST) in Slovenian undergraduate programs to assess the educational impact and quality of students’ contributions. 139 PT participated in a month-long data collection (Bioblitz) as part of their science courses. A quantitative approach was used to achieve our research objectives. Quality of the students’ observations and their activity patterns were analyzed using students’ observational data. Subsequently, their interests in nature and science, their self-efficacy in learning and doing science, and their self-efficacy in environmental action were assessed using a Likert scale questionnaire. The results indicate that the PT groups were similar in observation quality and activity patterns. Overall, observation quality was high (score 3.92/5 points) but limited by photo clarity and the lack of multi-angle photos. Both groups showed interest and confidence in the activity, with BSTs demonstrating greater confidence in science-related tasks. 25.2% of participants continued using the application after the activity concluded with significantly more BSTs than PSTs. These findings suggest that iNaturalist can serve as an effective tool for outdoor learning among diverse groups of preservice teachers. With appropriate training, they can use iNaturalist effectively even without an extensive background in biological sciences.</p>