Introduction: Research engagement during undergraduate medical education is increasingly recognized as essential for developing physician-scientists and fostering evidence-based practice. However, evidence regarding its effectiveness, challenges, and long-term impact remains fragmented. This systematic review synthesizes current evidence on outcomes, motivational factors, barriers, and effective practices in undergraduate medical research programs. Methods: Following PRISMA 2020 guidelines, we searched PubMed/MEDLINE, ERIC, Scopus, and Google Scholar for studies on undergraduate medical research engagement. Two reviewers screened 12,600 records and assessed 262 full texts for eligibility and quality (MERSQI, CASP). Eleven studies (n = 5,564 students, nine countries, 2010–2024) met the inclusion criteria. Owing to heterogeneity, a narrative synthesis was conducted across thematic domains. Results: Publication rates ranged from 15–55% (I2 = 87%), correlating with institutional resources. Students publishing before graduation were 1.9 times more likely to publish afterward (95% CI 1.6–2.3, p < 0.001). Experiential activities enhanced motivation (β = 0.45, p < 0.001) and self-efficacy (β = 0.38, p < 0.001), while grades showed no effect. Major barriers included curriculum demands (78.3%), limited funding (71.5%), and time constraints (61.7%). Prior academic performance did not predict research motivation. Discussion: Early research engagement fosters long-term scholarly identity but depends on mentorship, protected time, and funding rather than intrinsic motivation alone. Programs emphasizing authentic research experiences outperform grade-based models. Expanding access and addressing systemic barriers are essential to sustain research-oriented medical education and equitable scholarly development.