The Job Demands-Resources model highlights that aspects of the work environment that place high demands on employees are potential job stressors, which can reduce their levels of engagement with their work and organization. By contrast, social support for employees is a resource that can sustain their engagement and enable them to cope with high demands. We analyse the separate and combined effects of two key job demands and resources on the engagement of more than 4,000 senior public managers in ten European countries: organizational goal ambiguity, which may demotivate employees; and organizational social capital, which can prompt employees to share knowledge in constructive and helpful ways. The statistical results suggest that there is a negative relationship between goal ambiguity and engagement, and a positive one between social capital and engagement. Further analysis revealed that organizational social capital weakens the negative goal ambiguity-engagement relationship.