Background: Families do not fully disengage from care responsibilities following relatives' admissions to residential long-term (RLTC) care settings such as nursing homes. Caregiver stress, depression, or other key outcomes remain stable or sometimes increase following a relative's RLTC entry. Some interventions have attempted to increase family involvement after institutionalization, but few rigorous studies have demonstrated whether these interventions are effective in helping families navigate the potential emotional and psychological upheaval presented by relatives' transitions to RLTC environments. The Residential Care Transition Module (RCTM) provides six formal sessions of consultation (one-to-one and family sessions) over a 4-month period to family caregivers who have admitted a relative to a RLTC setting. Methods: In this embedded mixed methods randomized controlled evaluation, family members who have admitted a cognitively impaired relative to a RLTC setting are randomly assigned to the RCTM (n = 120) or a usual care control condition (n = 120). Primary outcomes include reductions in family members' primary subjective stress and negative mental health outcomes; secondary role strains; and residential care stress. The mixed methods design will allow for an analysis of intervention action mechanisms by "embedding" qualitative components (up to 30 semi-structured interviews) at the conclusion of the 12-month evaluation. Discussion: This evaluation will fill an important clinical and research gap by evaluating a psychosocial intervention designed for families following RLTC admission that determines whether and how the RCTM can help families better navigate the emotional and psychological challenges of residential care transitions. Trial registration: ClinicalTrials.gov (NCT02915939, prospectively registered).