This paper reports an empirical study of teacher development in the process of implementing an integrated science curriculum in a junior high school in China. Six science teachers with different subject backgrounds were invited to participate in this study. A pragmatic model of teacher learning that includes both cognitive and situated-learning perspectives was adopted with a focus on the professional, social and personal aspects of science teacher development. The data were collected from multiple sources, including in-depth interviews, direct classroom observations and participation in science teachers’ regular working meetings. The data analysis shows that the participants experienced various changes in the following aspects during the implementation of the integrated science curriculum: (1) updating science content knowledge; (2) reshaping the conception of science teaching; (3) establishing relationship with students; and (4) enhancing collegial interactions. The last part of this paper discusses these finding in the context of the literature on integrated science curricula and science teacher development.