People experiencing homelessness have higher rates of mental ill-health and substance use and lower access to health services compared to the general population. The COVID-19 pandemic led to changes in service delivery across health and social care services, with many adopting virtual or telephone support for service users. This paper explores the experiences of access to community-based mental health and substance use support for people experiencing homelessness during the COVID-19 pandemic. Qualitative telephone interviews were conducted with 10 women and 16 men (ages 25 to 71) who self-identified as experiencing homelessness in North East England between February and May 2021. With five individuals with lived experience, results were analysed using inductive reflexive thematic analysis. Reactive changes to support provision often led to inadvertent exclusion. Barriers to access included: physical locations, repetition of recovery stories, individual readiness, and limited availability. Participants suggested creating services reflective of need and opportunities for choice and empowerment. Community mental health and substance use support for people experiencing homelessness should ensure the support is personalised, responsive to need, inclusive, and trauma-informed. The findings of this research have important implications for mental health and substance use policy and practice for individuals who experience homelessness during a public health crisis.