Research self-efficacy is a key component of college students' career development. This study's purpose was to develop and begin to construct a validity argument for scores from the Sources of Research Self-Efficacy (SRSE) scale in college students. We explored validity evidence for SRSE scores from 719 undergraduate and graduate students based on test content, response processes, internal structure, relations to related variables, and consequences of testing. We present evidence from our development process for test content and response processes. Our statistical analyses suggest that a 20-item four-factor model is appropriate, with subscales representing Mastery Experiences, Vicarious Experiences, Social Persuasion, and Negative Emotional States. Subscale scores showed good internal consistency and correlated with both global research self-efficacy and research outcome expectancy scores. The SRSE shows promise as a measure of the various learning experiences that lead to students' research self-efficacy in university settings.