Objective Despite the increasing number of North Korean defectors, research on their mental health conditions and suicidal thoughts and behaviors has not been conducted systematically. We examined the prevalence and risk factors of suicidal thoughts and behaviors in North Korean defectors. Methods This study focused on 300 North Korean defectors recruited from regional resettlement centers in South Korea. In-person interviews based on the North Korean version of the Composite International Diagnostic Interview were conducted to diagnose mental disorders and assess suicidal thoughts and behaviors. Logistic regression analyses were performed to evaluate the association between suicidal thoughts and behaviors and socio-demographic variables, and DSM-IV mental disorders. Results Lifetime prevalence of suicidal ideation, plans, and attempts were 28.3, 13.3, and 17.3%, respectively. Female sex (OR: 2.0, 95% CI: 1.0–3.9), presence of health problems in the past year (2.6, 95% CI: 1.4–4.6), and absence of both South Korean acquaintances (1.9, 95% CI: 1.0–3.4) and North Korean family (1.7, 95% CI: 1.0–2.9) were associated with higher odds of suicidal thoughts and behaviors, after adjusting for participant age, sex, and education. Presence of a mental disorder was associated with a significantly increased odd of suicide ideation, plan, and attempt. Of all mental disorder categories, agoraphobia had the strongest association with suicidal ideation(6.5, 95% CI: 2.0–21.6), plans (7.7, 95% CI: 2.5–23.2) and attempts (12.0, 95% CI: 3.5–40.8). Conclusion Suicidal thoughts and behaviors among North Korean defectors are higher than the general population in South Korea, especially show high rates in transit countries. Further study should focus on the changes in suicidal thoughts and behaviors according to the settlement process and early prevention.