BACKGROUND No previous study could be found that examined the longitudinal association between suicidal ideation and the factors associated with it and that considered both individual and contextual characteristics simultaneously. This study examined whether variation in suicidal ideation is attributable to the administrative-area level and examined suicidal ideation and the factors associated with it at multiple levels, especially focusing on social capital. METHODS Longitudinal data of 5222 individuals and 2741 households in 25 administrative areas from the Wave 1 and Wave 2 of the Seoul Welfare Panel Study were used. RESULTS In the study, 2.7% of variation in suicidal ideation was attributable to the administrative area. The results also suggested that perceived helpfulness at individual level (odds ratio (OR) = 0.60; 95% confidence interval (CI) = 0.43, 0.83) and organizational participation at administrative-area level were associated with suicidal ideation (OR = 0.73; 95% CI = 0.53, 0.99). CONCLUSIONS Policy makers should consider laying down policies aimed at preventing suicide at administrative-area level as suicidal ideation of individuals is different between administrative areas. However, it should also be recognized that directing attention solely at administrative-area level is not efficient, as only small variations in suicidal ideation are attributable to this level. Decision makers need to consider policies promoting social capital, as it may play a role in reducing suicide risk.