AIMS: This study aimed to determine the effect of a multi-component mHealth intervention on patient activation and examine its predictors among older adults at risk of cardiovascular disease (CVD). METHODS AND RESULTS: This pilot randomized controlled trial compared two groups: Get FIT (control), who received healthy lifestyle counselling from a licensed health coach, a mHealth app (MyFitnessPal) with push alerts, and an activity tracker, and Get FIT + (intervention), who received the same interventions and had personalized text messages with 3- and 6-month follow-up periods. Patient activation was measured using the 13-item Patient Activation Measure; higher scores indicated better activation. Linear mixed-effects models were used to investigate between-group changes in outcomes across time. The participants (n = 54) mean age was 65.4 ± 6.0 years; 61% were female; and 61% were married. Baseline characteristics were comparable between groups. Significant improvements in mean patient activation scores were observed in the Get FIT + group at 3 months [mean 3.53 points, 95% confidence interval (CI) 0.11, 6.96; P = 0.043] and 6 months (mean 4.37 points, 95% CI 0.91, 7.83; P = 0.014), whereas improvements in the Get FIT group were non-significant. Adjusting for age, gender, education, employment, marital status, social support, smartphone confidence, and self-perceived health, we found that only social support was associated with higher patient activation overall (B = 5.14, 95% CI 1.00, 9.27; P = 0.015). CONCLUSION: The findings indicate that personalized text messaging can improve the self-care of older adults at risk of CVD. Findings also emphasize the importance of social support in the success of mHealth interventions for older adults. REGISTRATION: The study is registered in ClinicalTrials.gov (NCT03720327).