Although many colleges and universities use a wide range of criteria to evaluate and select admissions applicants, much of the variance in college student success remains unexplained. Thus, success in college, as defined by academic performance and student retention, may be related to other variables or combinations of variables beyond those traditionally used in college admissions (high school grade point average and standardized test scores). The current study investigated the predictive validity of a measure of motivational-developmental dimensions as a predictor of the academic achievement and persistence of college students as measured by cumulative undergraduate grade point average and retention. These dimensions are based on social-cognitive (self-concept, self-set goals, causal attributions, and coping strategies) and developmental-constructivist (self-awareness and self-authorship) perspectives. Motivational-developmental constructs are under-explored in terms of the predictive potential derived from their use in evaluating admission applicants’ ability to succeed and persevere despite the academic and social challenges presented by postsecondary participation. Therefore, the current study aimed to generate new understandings to benefit the participating institution and other institutions of higher education that seek new methodologies for evaluating and selecting college admission applicants. This dissertation describes two studies conducted at a large, urban public university located in the Northeastern United States. Participants included 10,149 undergraduate students who enrolled as first-time freshmen for the Fall 2015 (Study 1) and Fall 2016 (Study 2) semesters. Prior to matriculation, participants applied for admission using one of two methods: standard admissions or test-optional admissions. Standard admission applicants submitted standardized test scores (e.g., SAT) whereas test-optional applicants responded to four short-answer essay questions, each of which measured a subset of the motivational-developmental dimensions examined in the current study. Trained readers evaluated the essays to produce a “test-optional essay rating score,” which served as the primary predictor variable in the current study. Quantitative analyses were conducted to investigate the predictive validity of the “test-optional essay rating score” and its relationship to cumulative undergraduate grade point average and retention, which served as the outcome variables in the current study. The results revealed statistically significant group differences between test-optional applicants and standard applicants. Test-optional admission applicants are more likely to be female, of lower socioeconomic status, and ethnic minorities as compared to standard admission applicants. Given these group differences, Pearson product-moment correlation coefficients were computed to determine whether the test-optional essay rating score differentially predicted success across racial and gender subgroups. There was inconclusive evidence regarding whether the test-optional essay rating score differentially predicts cumulative undergraduate grade point average and retention across student subgroups. The results revealed a weak correlation between the test-optional essay rating score and cumulative undergraduate grade point average (Study 1: r = .11, p < .01; Study 2: r = .07, p < .05) and retention (Study 1: r = .08, p < .05; Study 2: r = .10, p < .01), particularly in comparison to the relationship between these outcome variables and the criteria most commonly considered in college admissions (high school grade point average, SAT Verbal, SAT Quantitative, and SAT Writing). Despite these findings, the test-optional essay rating score contributed nominal value (R2 = .07) in predicting academic achievement and persistence beyond the explanation provided by traditional admissions criteria. Additionally, a ROC analysis determined that the test-optional essay rating score does not predict student retention in a way that is meaningfully different than chance and therefore is not an accurate binary classifier of retention. Further research should investigate the validity of other motivational-developmental dimensions and the fidelity of other methods for measuring them in an attempt to account for a greater proportion of variance in college student success. / Educational Leadership