Undergraduate research experiences are critical for the talent development of the STEM research workforce, and research mentors play an influential role in this process. Given the many life science majors seeking research experiences at universities, graduate and postdoctoral researchers (i.e., postgraduates) provide much of the daily mentoring of undergraduate researchers. Yet, there remains little research on how postgraduates contribute to talent development among undergraduate researchers. To begin to address this knowledge gap, we conducted an exploratory study of the experiences of 32 postgraduates who mentored life science undergraduate researchers. We identified four factors that they perceived as enabling undergraduate researcher talent development: undergraduate researcher characteristics, research project characteristics, and mentoring implementation as well as outcomes for both the postgraduate and undergraduate. We then describe a team-based approach to postgraduate mentoring of undergraduate researchers that attends to these factors to provide an example that practitioners can adapt or adopt for their own research groups.