Instruction of team skills is quickly emerging as an important and missing dimension of engineering education. This project evaluated a new framework for guiding students in providing self- and peer assessments of their effectiveness in teamwork. This framework is the foundation for a new web-based tool that offers students structured feedback from teammates, along with personalized exercises and actionable strategies that guide targeted learning in the areas thereby identified. Specifically, the study documented in this report investigated whether the feedback framework, when used for intra-team self and peer feedback, increased students’ abilities to learn about and improve their team-effectiveness in executing design projects. The framework consisted of 27 competencies across three aspects of team-effectiveness: organizational, relational and communication competencies. The framework was tested in a randomized controlled experiment in a first-year engineering design class of 280 students against an unstructured feedback prompt. Students were asked to provide feedback at the mid-point of the course and to provide their thoughts on the utility of the feedback they received in an end-of-term survey. Student assessments were also compared to teaching assistant assessments.