Middle managers play key roles in hospitals as the bridge between senior leaders and frontline staff. Yet relatively little research has focused on their role in implementing new practices. The aim of this study was to expand the understanding of middle managers' influence in organizations by looking at their activities through the lens of two complementary conceptual frameworks. We analyzed qualitative data from 17 Veterans Affairs Medical Centers with high and low potential to change organizational practices. We analyzed 98 interviews with staff ranging from senior leaders to frontline staff to identify themes within an a priori framework reflecting middle manager activities. Analyses yielded 14 emergent themes that allowed us to classify specific expressions of middle manager commitment to implementation of innovative practices (e.g., facilitate improvement innovation, garner staff buy-in). In comparing middle manager behaviors in high and low change potential sites, we found that most emergent themes were present in both groups. However, the activities and interactions described differed between the groups. Middle managers can use the promising strategies identified by our analyses to guide and improve their effectiveness in implementing new practices. These strategies can also inform senior leaders striving to guide middle managers in those efforts.