Extant research suggests the effectiveness of Occupational Health Psychology (OHP) interventions depends on their design in the broader organisational context. While the field recognises that pre- and posttest evaluation do not sufficiently capture the complex dynamics around OHP interventions, complex multi-level OHP interventions are still scarce in the literature. As established intervention implementation frameworks suggest, it remains difficult to address this complexity in practice. The present position paper re-evaluates lessons learned from two complex European OHP intervention projects, by applying the Integrated Process Evaluation Framework (IPEF) and related theories to bridge the gap between the theoretically recognised complexity and practical challenges. The re-evaluations emphasise that programme-multilevel theories rooted in OHP-perspectives contribute to adequately hypothesising around systemic factors and mechanisms relevant to OHP interventions. Concretely, middle range theories that outline how an intervention’s mechanisms work within a specific context to produce certain outcomes are crucial. Additionally, strategically and actively involving key stakeholders at all levels of the system and across the different intervention phases improves the embedding of OHP interventions in organisations. We elaborate on these insights with seven concrete recommendations for complex OHP intervention research.