Previous studies on students' conceptions of learning science (COLS) have focused primarily on formal environments. In these studies, students' COLS were positively associated with their approaches to and outcomes for science learning. However, little research has been conducted to explore students' conceptions of learning science in informal environments (COLSIE), despite its importance to students' academic achievement. To fill this research gap, this study qualitatively and quantitatively explored Chinese primary school students' COLSIE. First, in Study I, interview data gathered from a group of 80 students were analysed using the phenomenographic method, and ten hierarchical categories of COLSIE emerged (e.g., communicating and explaining). Based on these categories, a survey was developed and distributed to another group of 414 students in Study II. Exploratory factor analysis was conducted to validate the survey, which revealed nine factors matching the ten categories except for the initial categories of applying and understanding. This study also revealed the commonalities and uniqueness of COLSIE in comparison with students' COLS in formal environments. The findings suggested that informal science learning experiences may strengthen students' impressions of science practices. Science educators are encouraged to provide their students with opportunities to engage with science practices in informal environments.