People experiencing homelessness (PEH) faced unique challenges during the COVID-19 pandemic, including changes to accommodation availability, societal restrictions impacting access to essentials like food, and services moving to online and remote access. This in-depth qualitative research aims to add to the existing, but limited research exploring how the pandemic affected PEH. 33 semi-structured qualitative interviews (22 with PEH during the pandemic and 11 with homelessness sector service providers) were undertaken in the United Kingdom between April 2021 and January 2022. Interviews were audio-recorded, transcribed and analysed using reflexive thematic analysis. To ensure consistency of coding, 10% of interviews were coded by two researchers. The PEH sample was 50% female, aged 24-59 years, 59% white British, and included people who had lived in hostels/hotels, with friends/family, and on the streets during the COVID-19 pandemic. Providers came from varied services, including support charities, housing, and addiction services. Five key themes were identified: (i) the understanding of and adherence to public health guidance and restrictions; (ii) the experience of people accommodated by the 'Everyone In' initiative; (iii) the impact of social distancing guidelines on PEH experiences in public spaces; (iv) the importance of social support and connections to others; and (v) how homelessness services adapted their provision. Policy makers and public health communicators must learn from PEH to maximize the effectiveness of future public health strategies. Housing providers and support services should recognize the implications of imposing a lack of choice on people who need accommodation during a public health emergency. The loss of usual support for PEH triggered a loss of ability to rely on usual 'survival strategies', which negatively influenced their health. This research highlights successes and difficulties in supporting PEH during the COVID-19 pandemic and informs planning for similar public health events.