This nonexperimental, longitudinal panel study was designed to test the predictive capacity of a grit intervention within a first-year seminar course that targeted academically underprepared students at a Mississippi community college. Extant pre- and post-grit scores for developmental students enrolled in the first-year seminar were analyzed for each cohort year between fall 2016 and fall 2018. The predictive capacity of post-grit scores on student success outcomes was also examined. The selected sample consisted of 129 first-time, full-time students enrolled in the first-year seminar with ACT sub-scores below 17 in English and Mathematics; all students in the sample had both pre- and post-grit scores on file. Research has shown grit is malleable through intervention with sustained long-term change, and intervention is especially effective for academically high-risk students and students of low- socioeconomic status. The first research question asked: Is there a difference in pre- and post-grit scores for developmental students enrolled in the first-year seminar? The amount of change in grit was not significant; however, chi-square analysis revealed significant proportionality changes from pre-test to post-test (p < 0.001). These findings suggest grit can change following intervention, but the difference in scores was not large. The second research question asked: Does grit predict success outcomes including first-term GPA, fall-to-spring persistence, fall-to-fall retention, and graduation for developmental students enrolled in the first-year seminar? No significant correlations were found. However, students that saw a grit score increase were more likely to be retained (p < 0.05).Several attribute variables were found to predict success outcomes: race (p < 0.01) predicted first-term GPA; race (p < 0.01), enrollment status (p < 0.01), and first-term GPA (p < 0.001) predicted persistence; gender (p = 0.05), enrollment status (p < 0.01), Pell eligibility (p < 0.05), first-term GPA (p < 0.05), and persistence (p < 0.001) all predicted retention; and full-time enrollment predicted graduation (p < 0.05). Overall, continued use of grit interventions within the first-year seminar is recommended, but retention efforts should place greater emphasis on providing support for Pell eligible students, racial and ethnic minorities, and academically underprepared students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]