Physicians' active engagement is a critical part of sustaining online health communities (OHCs) development. Gamification design can be leveraged to invoke physicians' gameful experience, better motivating their engagement in OHCs. However, it can also create inequality of economic returns among physicians, causing harm to these communities. Drawing on this operational paradox, this paper empirically examines both positive and negative effects of gamification on physicians and the contingent role of disparity in professional seniority on their engagement and inequality of economic returns, to advance knowledge of such practices. Although gamification design engages physicians and increases their income, the results indicate increased economic inequality among the physicians as a consequence. Considering physician's higher professional seniority in the same department, it weakens the positive effect of gamification design on their engagements but strengthens such effect on economic inequality. Managers are advised to carefully plan their gamification design in order to promote physician engagement in OHCs and avoid the related paradoxes.