IntroductionInadequate and varied quality of care in care homes has led to a proliferation of quality improvement (QI) projects. This study examined the sustainability of interventions initiated by such projects.MethodThis qualitative study explored the sustainability of seven interventions initiated by three QI projects between 2016 and 2018 in UK care homes and explored the perceived influences to the sustainability of interventions. QI projects were followed up in 2019. Staff leading QI projects (n=9) and care home (n=21, from 13 care homes) and healthcare (n=2) staff took part in semi-structured interviews. Interventions were classified as sustained if the intervention was continued at the point of the study. Thematic analysis of interview data was performed, drawing on the Consolidated Framework for Sustainability (CFS), a 40-construct model of sustainability of interventions.ResultsThree interventions were sustained and four interventions were not. Seven themes described perceptions around what influenced sustainability: monitoring outcomes and regular check-in; access to replacement intervention materials; staff willingness to dedicate time and effort towards interventions; continuity of staff and thorough handover/inductions in place for new staff; ongoing communication and awareness raising; perceived effectiveness; and addressing care home priorities. All study themes fell within 18 of the 40 CFS constructs.DiscussionOur findings resonate with the CFS and are also consistent with implementation theories, suggesting sustainability is best addressed during implementation rather than treated as a separate process which follows implementation. Commissioning and funding QI projects should address these considerations early on, during implementation.