While previous research has investigated the effectiveness of various second language (L2) writing instructional approaches upon students' writing performance, whether and how the instructional approaches relate to students' writing motivation and engagement remains largely unexplored. This study used the adapted Motivation and Engagement Scale for University/College students and investigated how the three L2 writing instructional approaches (i.e. product-, process-, and genre-oriented) were associated with L2 students' writing motivation and engagement. A sample of 1,190 students from 35 universities in China participated in the study. Results show that the product-oriented approach induced both adaptive and maladaptive motivation and engagement whereas the process-oriented approach led to student engagement in writing with limited impact on motivation. The genre-oriented approach emerged as the one that best promoted students' adaptive motivation and engagement in L2 writing. The findings shed light on the motivational potentials of various L2 writing pedagogies and provided insights for how students' writing motivation and engagement can be promoted with relevant L2 writing instructional approaches.