Writing apprehension has always been considered a serious obstacle for L1 and L2 teachers and students alike and, in most cases, it could impede students’ language learning. Accordingly, a considerable number of students develop a great concern about and negative attitudes toward writing, and avoid situations where writing is required. The treatment procedure employed in this study, which was assumed to reduce students’ writing apprehension, was a collaborative approach to learning. In this approach student writers work collaboratively in groups to explore, analyze, and negotiate meaning and solve problems in a non-threatening atmosphere. Therefore, this study was intended to investigate the impact of collaborative learning on L1 and L2 college students’ apprehension about and attitudes toward writing. Three hundred forty nine L1 students and 12 L1 writing teachers, and 77 L2 students and 3 L2 writing teachers participated in this study. Both L1 and L2 Students responded to the Daly-Miller Writing Apprehension Test twice, once as a pretest and another time as a posttest.