Poor performance in introductory courses and lack of individualized assistance may contribute to college non-completion. This research aims to identify the effects of increased, personalized instructor feedback on performance in introductory college courses. We use an experimental method similar to Carrell and Kurlaender (2020), where poorly-performing students in large lectures are randomized to receive additional feedback through email about their course performance along with encouragement and methods for improvement. Half of the treated students receive feedback from their teaching assistant, while the other half of treated students receive feedback from their instructor. We compare the efficacy of feedback from instructors to feedback from teaching assistants. We test the intervention’s effects on overall course performance, frequency of help-seeking, and perceptions of instructor and teaching assistant quality. Identified effects have implications for the role of feedback in student success and whether feedback from instructors or teaching assistants is more effective. The low-cost nature of the intervention means that it could be easily implemented elsewhere and scaled rapidly.