(1) Background: Hypertension (HTN) affects ~50% of adults and is a major risk factor for stroke and cardiovascular disease. In 2017, the SPRINT trial outcomes led to lowering of HTN cutoffs by the American College of Cardiology (ACC) and American Heart Association (AHA). The Joint National Committee (JNC8) and National High BP Education Program recommend that lifestyle modifications be used as first-line HTN treatment. Chronic stress is a risk factor for HTN and cardiovascular disease. A recently completed 12 month randomized controlled trial (RCT) of a breathing meditation smart phone app (Tension Tamer, TT) involving JNC8 designated pre-HTN adults provided an opportunity to examine its impact upon individuals now classified as having stage 1 HTN. The TT app captures continuous real-time heart rate (HR) from a user’s fingertip placed over a video camera lens during sessions. Users receive immediate feedback graphs after each session, showing their HR changes. They also receive motivational and social reinforcement SMS text messages the following day based upon levels of adherence. We conducted ancillary analyses of a 2-arm, 12-month, small-scale efficacy RCT among a subgroup of our total sample of participants, who are now classified as having stage 1 non-medicated systolic HTN. Primary outcome was change in resting systolic blood pressure (SBP). Secondary outcomes were change in resting diastolic blood pressure, adherence to the TT protocol, and perceived stress levels. (2) Methods: 30 adults (mean age: 45.0 years; 15 males; 16 White; 14 Black) with ACC/AHA 2017 defined systolic HTN (130-139 mmHg) on 3 consecutive sessions (mean SBP: 132.6 mmHg) were randomly assigned to TT or lifestyle education program delivered via smartphone (SPCTL). Each group received a twice-daily dosage schedule of TT or walking (month 1: 15 min; months 2 and 3: 10 min; months 4-12: 5 min). (3) Results: Mixed modeling results revealed a significant group x time effect for SBP (p<.01). The TT group showed greater SBP reductions at months 3 (-8.0 vs. -1.9), 6 (-10.0 vs. -0.7), and 12: (-11.6 vs. -0.4 mmHg; all -values <0.04). (4) Conclusion: The TT app was beneficial in reducing SBP levels among adults with stage 1 systolic HTN. The TT app may be a promising, scalable first-line tactic for stage 1 HTN. Preparations are underway for an efficacy RCT involving uncontrolled stage 1 HTN patients.