In response to growing concerns about students’ low aspiration for science-related careers, more understanding on how student science motivation is related to science career aspiration is needed. This study utilised a person-centred approach to investigating the association between students’ science-related motivation profiles and their science career expectation using the 2015 Programme for International Student Assessment (PISA) data set. Analysing responses from 9841 15-year-old students in China through Latent Profile Analysis (LPA), the study found that: (1) five distinct students’ motivation profiles were identified based on science-related motivation factors; (2) significant variations were observed in science career expectations across students’ motivation profiles, and different profiles predicted science career expectations differently; and (3) the perceived instructional practices and science learning engagement, social and economic status, and students’ gender significantly predicted students’ motivation profiles differently. These research findings contribute to new insight on the non-linear relationships between science-related motivation and science career expectation, and how student motivation profiles are impacted by demographic and context factors such as instructional practices, learning engagement, students’ social and economic status, and gender.