OBJECTIVE: To identify strategies to facilitate the sustainability of a quality and safety improvement collaborative: the Safer Patients Initiative (SPI) and its successes. DESIGN: A qualitative interview study with a repeated sample at two time points. SETTING: Twenty organizations participating in the SPI programme in the UK. PARTICIPANTS: Twenty principal SPI programme coordinators took part in interviews towards the end of the supported phase of the programme, 12 of which were interviewed again a year later, along with another three replacement programme coordinators, totalling 35 interviewees across the two time points. MAIN OUTCOME MEASURES: Programme coordinators' perceptions of facilitating strategies to the sustainability of the collaborative and its gains. RESULTS: Qualitative analysis identified three overarching factors for the sustainability of SPI: (i) using programme improvement methodology and measurement of its outcomes; (ii) organizational strategies to ensure sustainability and (iii) alignment of goals with external requirements. Within these were eight themes identified by the coordinators as helping to sustain the efforts of the SPI programme and its successes. CONCLUSIONS: This study has presented what principle programme coordinators across 20 NHS organizations considered to be the key strategies to sustain their own improvement programme and its successes, during the supported phase of the programme and 1 year on. Recommendations are to consider these practical strategies in order to improve chances of maintaining changes and continuing a quality improvement programme beyond the formal cessation of the intervention.