Most interventions for mental health and psychosocial support (MHPSS) have been developed in contexts and with populations that differ significantly from the realities of migration. There is an urgent need for MHPSS in transit; however, transit-specific aspects of MHPSS provision are often neglected due to the inherent challenges transit poses to traditional conceptualizations of practice. The Delphi method, which consisted of three iterative rounds of surveys, was applied with the goal of identifying challenges to and adaptations of MHPSS in the transit context. Twenty-six MHPSS providers working with refugees in 10 European transit countries participated; 69% of participants completed all three survey rounds. There was consensus that a flexible model of MHPSS, which can balance low intensity interventions and specialized care, is needed. Agreement was high for practice-related and sociopolitical factors impacting MHPSS in transit; however, the mandate of MHPSS providers working in the transit context achieved the lowest consensus and is yet to be defined. There is a need to rethink MHPSS in the refugee transit context. Providing MHPSS to refugees on the move has specificities, most of which are related to the instability and uncertainty of the context. Future directions for improving mental health protection for refugees, asylum seekers, and migrants in transit are highlighted.