Myasthenia gravis (MG) is a rare autoimmune neuromuscular disorder that can result in serious exacerbations requiring hospitalization. Recent regulatory alerts have raised concern about potential links between statin use and MG onset or worsening, but evidence remains limited. We evaluated the association between statin initiation and MG-related hospitalization using a nationwide claims database from South Korea (2007–2023). Patients aged ≥20 years with confirmed MG diagnosis and at least one MG-related hospitalization were included. A self-controlled case series (SCCS) design was applied, with 365-day observation windows before and after statin initiation. Risk intervals were defined as 1–30, 31–90, 91–180, and 181–365 days post-initiation, and incidence rate ratios (IRRs) were estimated using conditional Poisson regression. Among 204 statin-naive MG patients, statin initiation was associated with significantly elevated risk of MG-related hospitalization within the first 30 days (IRR 1.78, 95% CI: 1.12–2.83). No significant increase was observed thereafter. Subgroup analyses indicated higher risk in patients aged ≥65 years (IRR 3.19, 95% CI: 1.03–9.86) and males (IRR 2.41, 95% CI: 1.22–4.76). Sensitivity analyses yielded consistent results. Statin initiation should be cautiously considered in MG patients, particularly in high-risk subgroups such as older adults and males.