Background: No real-world randomised controlled trials (RCTs) have explored the effectiveness of lifestyle interventions based on multiple behaviour change theories and using combined digital and group-based face-to-face delivery to improve risk factors for type 2 diabetes (T2D). Methods: We conducted a one-year, multi-centre, unblinded, pragmatic RCT in primary healthcare using the habit formation, self-determination, and self-regulation theories among 2907 adults aged 18–74 years at increased T2D risk randomised into a digital lifestyle intervention group (DIGI, n = 967), a combined digital and group-based lifestyle intervention group (DIGI+GROUP, n = 971), and a control group receiving usual care (CONTROL, n = 969). We collected data on primary outcomes (diet quality by Healthy Diet Index [HDI], physical activity, body weight, fasting plasma glucose, 2-hour plasma glucose) and secondary outcomes (sedentary time, waist circumference, fasting plasma insulin) using digital questionnaires, clinical examinations, fasting blood tests, and 2-hour oral glucose tolerance tests. Main statistical analyses were performed using linear mixed-effects models adjusted for age, sex, and province. This RCT was registered with ClinicalTrials.gov, NCT03156478. Findings: The 2907 participants assigned were recruited between March 1st, 2017, and February 28th, 2018. Diet quality improved more (3·2 vs. 1·4 HDI points, p