Evidence of the association between effort reward imbalance (ERI) and suicidal ideation is sparse. This study examined the influence of ERI at work on suicidal ideation and the mediating effect of depressive symptoms.There were 4963 workers aged 50+ without suicidal ideation at baseline in the Survey of Health, Aging and Retirement in Europe, these workers were followed-up for 8-years to detect incident suicidal ideation. ERI was measured by a short ERI questionnaire. Suicidal ideation was evaluated by one item derived from the 12-item Europe-depression scale, and depressive symptoms were assessed by the remaining 11 items in the scale. Cox models were employed to explore the relationship adjusting for potential confounders. Mediation analysis was used to test the mediating effect of depressive symptoms.A significantly higher incidence of suicidal ideation was related with high effort (HR = 1.51) and low reward (HR = 1.42), respectively. A high effort-low reward imbalance was associated with even higher risk of suicidal ideation (HR = 1.96) as compared to low effort-high reward combination. The association was varied by gender, region, education and household income. Depressive symptoms mediated a modest proportion (natural indirect effect 14.4%) of the total association between ERI and suicidal ideation.Suicidal ideation definition based on self-administered questionnaires which could lead to false negatives. And some unmeasured confounders might have biased the results.Efforts in promoting balanced effort-reward at work may reduce suicidal ideation among working population aged 50+. Avoiding depressive symptoms may further enhance such efforts.