This study investigated how elementary students’ science-related affective characteristics and their perception of measurement changed following participation in citizen science activities through a GLOBE program. Before and after the activities, test of positive experiences about science (PES) and perception of measurement were conducted with twelve fourth grade students. In addition, the teacher who participated in the GLOBE program with students observed and recorded the students’ involvement, conversation and behavior to qualitatively analyze the value of the program and the students’ perceptions of measurement. After the end of the program, an open questionnaire was conducted to fill any gaps in these observations. The results showed that citizen science activities had a positive impact on elementary students’ science-related affective characteristics. In all areas of PES test, the post-test scores were higher than the pre-test results, and a statistically significant difference was seen in the ‘science learning motivation’ area. Furthermore, students’ perception of the value and meaning of measurements was seen to deepen through ongoing global environmental data measurement activities. And their understanding of various units of measurement and numerous situations in which they might need to make measurements was also elaborated.