The study contributes to the debate in the HRM literature by examining the role of trust in management in moderating the effect of HRM practices on employee attitudes. The novelty of the study lies in our interest in assessing this relationship not only on a system of HR practices, but also considering whether the influence varies according to specific ‘bundles’ of practices. Adopting a Structural Equation Modelling approach, we first test the moderation using an HRM index of seven practices on a sample of 9,000 employees from 46 Italian organisations. Then, following the AMO approach, we assess the relationship on three ‘bundles’ of practices, one oriented to increasing ability, another motivation and the third opportunity to participate. Results confirm the moderation with the overall HRM index. Interestingly, the effect varies depending on the HR bundles, being significant only with the motivation practices and not relevant in the other two bundles.