The HOPE 4 trial (Heart Outcomes Prevention and Evaluation 4) investigated the effectiveness of a comprehensive, collaborative model of care, implemented in Colombia and Malaysia, which aimed to reduce cardiovascular disease risk in individuals with hypertension. One component of this intervention was the nomination of a treatment supporter, where participants could select a family member or friend to assist them with their care. The purpose of this study was to investigate the impact of these individuals on participant outcomes, as well as the relationship dynamics between participants and their treatment supporter. Participants in the HOPE 4 intervention group with baseline and 12 months of follow-up were included for analysis. They were divided into Every Visit (n=339) and <Every Visit (n=268) groups based on whether they had a treatment supporter for all 5 or for <5 follow-up visits, respectively. Outcomes were stratified between groups and tested for significance using a generalized linear mixed-effects model. A survey investigating participant satisfaction with their treatment supporter was administered at 12 months. Groups were majority female (53% versus 62%) with a mean age of 63 and 66 years. Country of origin differed between groups (22% versus 86%; Colombia). A 15.5% ([95% CI, 6.2%-24.8%] P=0.004) greater increase in statin medication use was reported in the Every Visit group at 12 months compared with the <Every Visit group. Sixty-one percent versus 48.2% of participants reported high medication adherence at 12 months (P<0.003). The difference in change in systolic blood pressure between groups was not found to be significant at 12 months, though it favored the Every Visit group (-2.3 [95% CI, -6.1 to 1.5]; P=0.045). The majority of survey respondents from either study group strongly agreed that having a treatment supporter positively influenced their health. Long-term support from a nominated treatment supporter was associated with improved adherence, risk factor management, and medication use among individuals with hypertension. URL: https://www.clinicaltrials.gov; Unique identifier: NCT01826019.