Aims/hypothesis <p>This multicentre prospective observational cohort study aimed to evaluate real-world changes in glycaemic and person-reported outcomes after 1 year’s use of Control-IQ technology in adults with type 1 diabetes.</p> Methods <p>Adults who started with Control-IQ between December 2021 and December 2022 were consecutively recruited in 13 Belgian diabetes centres. Data were collected at start and after 4, 8 and 12 months. The primary endpoint was the evolution of time in range (TIR; glucose levels of 3.9–10.0 mmol/l). Data are reported as mean ± SD or least-squares mean (95% CI).</p> Results <p>A total of 473 adults were included, with a mean age of 38.5&#xa0;±&#xa0;13.1 years and of whom 57.3% were female. TIR increased from 58.8% (95% CI&#xa0;56.7, 60.9) at start to 70.9% (69.1, 72.8) at 12 months (<i>p</i>&lt;0.001). HbA_1c decreased from 57.3 mmol/mol (56.1, 58.5) (7.4% [7.3, 7.5]) to 49.5 mmol/mol (48.5, 50.6) (6.7% [6.6, 6.8]) and time &lt;3.9 mmol/l from 4.2% (3.9, 4.6) to 1.9% (1.8, 2.1) (all <i>p</i>&lt;0.001). Participants scored better on the Hypoglycaemia Fear Survey version 2 worry (22.5 [21.3, 23.7] vs 18.1 points [17.0, 19.3]), the Problem Areas in Diabetes - Short Form (7.2 [6.7, 7.8] vs 6.1 points [5.5, 6.7]), and the Diabetes Treatment Satisfaction Questionnaire status (25.5 [24.8, 26.2] vs 31.0 points [30.4, 31.6]) (all <i>p</i>&lt;0.001). The number of self-reported severe hypoglycaemia events (37.5 [21.3, 65.9] vs 15.7 [9.7, 25.3] events per 100 person-years, <i>p</i>=0.002) and work absenteeism days (116.3 [42.8, 315.5] vs 69.3 [25.4, 189.2] days per 100 person-years, <i>p</i>=0.034) decreased.</p> Conclusions/interpretation <p>One-year use of Control-IQ was associated with better glucose management, improved diabetes-related quality of life, more treatment satisfaction, less severe hypoglycaemia and less work absenteeism in adults with type 1 diabetes.</p> Trial registration <p>ClinicalTrials.gov NCT04414280</p> Graphical Abstract <p></p>