Focusing on community college transfer students who declared a STEM major at their initial transfer to a four-year research university, this study examined the extent to which students' sociodemographic characteristics and academic factors were related to STEM persistence and attrition. This study tracked multiple cohorts of transfer students matriculated at the four-year university between fall 2007 and fall 2014, and used data drawn from their transcript records. The findings indicated that STEM switchers, who obtained a non-STEM degree within six years of their initial transfer, were more likely to be older learners, female, and of non-Asian race/ethnicity than STEM persisters, who earned a STEM degree within six years. STEM Leavers, who did not earn any degree within six years, were more likely to be older, non-Asian, first-generation, and had a low or middle family income than STEM persisters. The study also found that STEM switchers and leavers were more likely to transfer over a lower number of courses, attempted fewer courses in the first semester, withdrew one or more courses, and received a lower semester GPA. In terms of mathematics preparation, STEM switchers and leavers were less likely to complete Calculus I or more advanced courses. The study contributes to the literature on STEM persistence and attrition, especially for STEM aspirants who transferred from community colleges to four-year universities. The findings also provide new knowledge about STEM attrition by comparing students who departed from STEM with or without earning a non-STEM degree.