This study examines whether Customer Relationship Management (CRM) data can support pharmaceutical sales efficiency and marketing in Korea. Three datasets from Company A were analyzed: 56,741 CRM visit records (Jan–Jun 2026), 43,471 sales records (Jan 2025–May 2026), and a CRM-based handover document covering four hospitals in Seoul. An account-month analysis (n = 755) showed a significant association between visits and sales (Pearson r = 0.545; Spearman ρ = 0.627; both p < 0.001). OLS analysis indicated that each additional visit was associated with a KRW 63,200 increase in monthly sales. Fixed-effects decomposition identified between-account (r = 0.575) and within-account effects (r = 0.119, p < 0.01), suggesting that resource allocation and visit intensity are both related to sales performance. In the four-hospital case study, average monthly sales increased from KRW 40.1 million to KRW 47.2 million during the assignment period (+17.5%; Welch’s t = 3.62, p = 0.003). In the first month after handover, the successor achieved KRW 49.2 million in sales, 28% higher than the same month of the previous year. These findings suggest that CRM can support handover, call-plan design, resource reallocation, and evidence-based pharmaceutical marketing under the K-Sunshine Act.