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).