Annually, millions of Americans experience homelessness. Hypertension (HTN) is one of the most common conditions among persons experiencing homelessness (PEH) but is often uncontrolled; 40.1% of hypertensive PEH have uncontrolled blood pressure (BP) compared to 24.8% of hypertensive adults in the general population. PEH face multiple barriers to therapeutic lifestyle changes that complicate their HTN management. Strategies targeting self-management behaviors and counseling to support adherence to medications and lifestyle changes contribute to better BP control and significant cardiovascular risk reduction. However, these strategies are not available or accessible to the PEH. At the patient level, educational interventions with behavioral support through continued patient contact over months are effective in the treatment of chronic diseases including HTN. The mHealth strategies including short messaging service (SMS) texting have been shown to improve adherence to BP medications and BP control and were feasible and acceptable among hypertensive adults. Majority of the PEH have access to mobile phones that can receive and send SMS texts. Considering mobility of the PEH, we propose that an mHealth strategy using SMS texting could be used as a platform for better communication and information management for BP control, facilitate coordination of care, support behavior changes, and improve targeted outreach. The mHealth strategies for HTN have never been evaluated in the PEH despite the growing evidence of their effectiveness and the accessibility of mobile phones among PEH. This study will test this strategy and pave the way for its utilizations in the health settings where the PEH seek care, and has potentials for adaptation for control of other chronic diseases among PEH. This study will be implemented in shelter-clinics in New York City (NYC) and in collaboration with community organizations making sustainability of the intervention effects and its scalability feasible. We propose a mixed methods study: AIM1: To assess patients’ and providers’ attitudes, acceptability, and experience of a 6-month mHealth SMS texting for HTN management in hypertensive PEH age 21 or older with uncontrolled BP in NYC’s shelter-clinics. We will use semi-structured interviews using random and criteria sampling of the PEH (n=30) and providers (n=20). AIM2: To evaluate the efficacy of a 6-month SMS texting targeted on HTN management (INT) versus an attention control (CL) on changes in systolic BP (SBP) and diastolic BP (DBP) and adherence to BP medications and appointments at 6 months in hypertensive PEH with uncontrolled BP age 21 or older (n=120). H1) Those randomized to the INT (n=60) will exhibit at least 8 mmHg reduction in either SBP or DBP compared to those randomized to the CL (n=60) at 6 months. H2) The INT group will exhibit better adherence to BP medications and appointments compared to those in the CL at 6 months. BP readings and adherence to appointments a...