Transitioning to civilian life after military service can be challenging for both Veterans and their families. Accessible mental health services are crucial during this period to provide support. The objective of this review was to conduct a rapid review to capture the barriers and identify facilitators that influence access to mental health services for Veterans and their families during the post-service transition period. This review was conducted using the Cochrane Handbook for Systematic Reviews of Interventions as a methodological framework and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Rapid Review (PRISMA-RR). A total of 60 articles and 67 independent samples were included in the final data analyses. Across the included articles, this review identified 23 barriers and 14 facilitator themes. Issues navigating the mental health care system was identified as the main challenge among Veterans and their families, and those who received support navigating the system identified this as a significant facilitator. Applying the Theoretical Domains Framework, most of the identified barriers and facilitators were categorized into environmental context and resources domain. The heterogeneity in Veterans' and Veteran families' experiences with mental health care-seeking may suggest that access to mental health care for Veterans and Veteran families cannot be solved by addressing one type of barrier alone. Instead, coordinated efforts to address prioritized systemic, logistical, social, and inter-/intrapersonal obstacles are essential for improving access and optimizing mental health care outcomes. These insights underscore the complexity of considerations for Veterans and families accessing mental health care.