Behavioral states1can be transferred to others, leading people to behave in ways similar to those around them. Can this phenomenon of behavioral contagion be seen in the workplace? Using employees' organizational social media data and their workplace hierarchical network structure, we studied contagion across a large multinational corporation, focusing on an important workplace behavior - employee engagement. We measured employees' engagement based on their word choice in organizational social media, and we applied a longitudinal statistical technique which controls for homophily, employees' traits and prior expressions of engagement. We found that engagement and disengagement spread from one employee to another with direct peers exerting the strongest influence. While engagement-spread was more powerful laterally among people at the same organizational level, disengagement-spread followed the vertical managerial chain. Further, we found that disengaged co-workers exerted a stronger influence on employee's future engagement compared to the engaged co-workers. Our results suggest the need for organizations to sense and address workplace disengagement promptly. Moreover, our findings offer opportunities for using workplace interventions to promote engagement and mitigate disengagement.