The purpose of this paper, based on Social Cognitive Theory, is to emphasize the proactive role of self-efficacy which is hypothesized to predict work engagement, not only directly, but also indirectly through positive changes in employee’s perceptions of social context (PoSC); namely, perceptions of one’s immediate supervisor, colleagues and top management. A sample of 741 employees of an Italian communication service company completed two questionnaires, with a time interval of three years. Results revealed that, as expected: first, initial self-efficacy predicts work engagement three years later; and second, positive changes in employee’s perceptions of the social work context across the three year period, mediates the relationship between self-efficacy and work engagement. The significant role of self-efficacy as a direct and indirect predictor of work engagement suggests the development of training programs centered on the main sources of self-efficacy, specifically focused on the social work domain. This research provides evidence of the substantial contribution of self-efficacy to work engagement over time. Moreover, the results also support the beneficial effects of self-efficacy through its influence on the improvements in the individuals’ perceptions of their social context (read more).