question: Teamwork is an important skill valued by corporate employers across the globe. As such, it is crucial for students to learn teamwork for the purpose of securing a job and performing well in corporate environments. In addition to certain technical skills, essential 21st-century skills include communication, collaboration, critical thinking, and creativity. A well-known learning theory that helps students learn these skills is cooperative learning. Cooperative learning posits that when students collaborate within teams to solve complex problems, their creativity and critical thinking skills are improved as a result. Implementing cooperative learning in the past several months has been challenging due to the COVID-19 pandemic. The sudden shift from face-to-face to online instruction, has left a void for newer pedagogical approaches to teach teamwork. In this full paper, we investigate the impact of cooperative learning during the Spring 2020 semester by studying team retrospectives written by students enrolled in a system analysis and design course. The pedagogical foundation for the system analysis and design course was cooperative learning. The course required students to work in teams to develop a software prototype. The project was divided into four milestones and each team was required to submit a team retrospective detailing overall planning, task allocation, group processes, and strategies for improvement. The first two milestones were completed during face-to-face instruction, while teams met online for the last two milestones due to the shift to online instruction. To investigate team effectiveness, a rubric based on the Goals, Roles, Processes and Interpersonal relations (GRPI) model of team effectiveness was created and team retrospectives were scored using that rubric. We used a mixed-method approach to explore the following research questions: 1) What was the impact on team effectiveness when instruction changed from face-to-face to online due to the COVID-19 pandemic? 2)What strategies were adopted by teams to navigate the sudden change in instruction? To address the first research question, we performed inferential statistics to compare the impact of team effectiveness between face-to-face and online instruction. To address the second research question, we conducted a thematic analysis to understand the qualitative differences of team effectiveness for face-to-face and online instruction. Our results demonstrate a significant increase in teamwork effectiveness for online instruction. In addition, our thematic analysis shows particular strategies adopted by teams that led to improved team effectiveness in the online instruction environment. © American Society for Engineering Education, 2021