Content and language integrated learning (CLIL) programs impose enormous demands on teachers, who are expected to integrate the two aspects pedagogically. Content and language teachers are thus encouraged to collaborate to help students master content knowledge and develop their additional language (L2) proficiency simultaneously. To reveal whether such teacher collaboration (TC) is beneficial, researchers have also attempted to examine its effectiveness on student learning. Situated in a Chinese tertiary classroom, this quasi-experimental study investigated how TC affected student learning by recruiting a content instructor, a language expert, and 50 students in two intact drama classes (n = 25 each). The impact of TC on student learning was captured by two character analyses written by the two groups of students before and after the intervention which lasted throughout the 13-week drama course. Results from inferential statistics and textual analysis showed that students in the experimental group improved their writing in both content and language aspects as compared to their peers in the control group. Such findings show that TC is conducive to student learning in CLIL and yield significant implications for CLIL pedagogy.