Hypertension is an important risk factor of cardiovascular diseases, the leading cause of death worldwide. Adverse effects of psychosocial factors at work might increase the risk of masked hypertension, but evidences are still scarce. The objective of this study is then to determine whether adverse psychosocial work factors from the effort-reward imbalance (ERI) model are associated with the prevalence of masked hypertension in a population of white-collar workers. White-collar workers were recruited from three public organizations. Blood pressure was measured at the workplace for manually operated measurements (mean of the first three readings taken by a trained assistant) followed by ambulatory measurements (mean of all subsequent readings taken during the working day). Masked hypertension was defined as manually operated BP < 140/90 mm Hg and ambulatory BP ≥ 135/85 mm Hg. ERI exposure at work was measured using Siegrist's validated questionnaire. Blood pressure readings were obtained from 2369 workers (participation proportion: 85%). ERI exposure (OR: 1.53 (95% CI: 1.16-2.02) and high efforts at work (OR: 1.61 (95% CI: 1.13-1.29) were associated with masked hypertension, after adjusting for sociodemographic and cardiovascular risk factors. Workers exposed to an imbalance between efforts spent at work and reward had a higher prevalence of masked hypertension. High efforts at work might be of particular importance in explaining this association. Future studies should be designed to investigate how clinicians can include questions on psychosocial work factors to screen for masked hypertension and how workplace interventions can decrease adverse psychosocial exposures to lower BP.