Introduction: Closed Loop (CL) technology has the potential to prevent hypoglycaemia and reduce glycaemic variability in type 1 diabetes (T1D). Its maximum benefit will depend largely on uninterrupted and appropriate use of the device by the person with T1D. Acceptability and perceived costs/benefits of CL will therefore be key factors for implementation. Objectives: This qualitative study explored participants’ experiences after four nights Home Closed Loop (CL) Insulin Delivery System use vs. Sensor Augmented Pump Therapy with Low-Glucose Suspend in a randomised cross-over trial. Methods: Ten adults completed the trial between April 2014 and March 2015; median age 37.5 years (range 32-62); diabetes duration 31 years (range 8-36); five were women. Semi-structured interviews were conducted on day five, after four consecutive nights of CL at home. Interviews were audio-recorded, with transcriptions imported into NVivo10 for thematic analysis. A coding framework was developed to identify themes and subthemes. Results: When asked about the four nights’ CL experience, the most common observation was the ‘flat-line’, showing stable overnight glucose levels. Although most reported technical glitches during one or more nights, few safety concerns were raised. If any, these related to feeling unsure whether the system would respond in time to falling glucose. However, confidence increased when they observed how the CL stopped insulin delivery when their glucose was trending down, how (when switching to CL at night) the CL dealt with high glucose levels. Compared with their current insulin pumps (and, for some, sensors), participants reported the following benefits: less decision making, resulting in few human errors; fewer alarms, as the CL kept glucose levels within target overnight; not having to cope with the consequences of hypo- and hyperglycaemia (e.g. feeling sick post event), due to less glucose variability. Participants found the CL easy to use, but noted that this might be different for people who are less ‘tech savvy’. Conclusions: Participants gave a very positive evaluation of the CL in the home. They were impressed with how well the CL responded to their glucose levels, although they noted that further improvement of the technology will enhance the user’s experience.