We examined the effects of in-class writing instruction, practice, peer review, and feedback on writing skills of undergraduates enrolled in a general psychology course. We rated writing for grammar, writing style, mechanics, and American Psychological Association referencing style. Significant differences emerged on the 4 writing skill domains (p less than 0.001). Improvement occurred immediately for referencing, whereas other skills did not improve significantly until the 4th paper. The results show that teaching writing in content courses such as general psychology can yield significant improvement in students' writing. We believe that writing instruction by psychology professors is worth the time and effort to help undergraduate psychology students develop better writing skills.