Faculty at all types of colleges and universities struggle with how smartphone use may enhance or diminish their pedagogy, in part because evidence-based data is lacking for most types of classrooms. Thus, we conducted a thorough investigation in an introductory biology lab course to determine how smartphones affected myriad aspects of student learning and engagement. There were no significant differences in exam scores, the amount of time spent studying, occasions students were off task, or questions asked to the instructor. There were, however, significant differences in several measures of engagement and time management; students allowed to use their smartphones spent 64% less time in peer-to-peer interactions, 46% less time taking notes, 70% less time handling specimens, and 31% less time in lab compared to students who were not allowed to use smartphones. Because these behaviors, in particular peer engagement and note taking, are fundamental skills best developed early in a successful undergraduate career, our results suggest smartphone use should be minimized in introductory biology laboratories.