Background: Systemic arterial hypertension is the main modifiable risk factor for development of cardiovascular disease, which is the number one cause of death in high income countries and is increasingly becoming a cause of concern in Sub-Saharan Africa (1). Awareness, management and overall control of hypertension in Sub-Saharan Africa is poor (2,3). Poor control stems from various causes; one being patient non-adherence with medication, a factor amenable to modification. The use of mobile health for behavioural change from low resource settings is gaining widespread use in management of communicable diseases (4,6). Mobile phone has the potential to significantly influence patients to improve adherence to antihypertensive medication thereby leading to better control of hypertension and forestalling complications (6). In Kenya, there is, to date, no evidence of a trial on mobile text messaging to determine whether there is any change in adherence rates to antihypertensive therapy in patients. Objective: The primary objective is to set-up and carry out a Hypertension Short Message Service system to assess whether sending weekly reminders as text messages via a mobile phone will improve adherence rates to antihypertensive treatment, which has been found to translate to improved blood pressure control. Methods: The study was a Randomised Controlled Trial with an intervention arm and control arm involving hypertensive patients seeking treatment at the Family Medicine Clinic at Aga Khan University Hospital, Nairobi. Results: Prior to carrying out the Hypertension Short Message Service system the level of adherence to antihypertensive therapy in the intervention group was 60.3% compared to an adherence rate of 61% in the control group. Six weeks following the intervention, the adherence rate increased by12.4% and 5.3% in the intervention and control groups respectively. The intervention had a statistically significant effect represented by a 7.1% improvement in adherence rate in intervention arm above the control arm (p < 0.001). Diastolic blood pressure measurements reduced from an average of 87.9 mmHg to 81.8 mmHg in the intervention group compared to a reduction from 86.8 mmHg to 82 mmHg among patients in the control group. Systolic blood pressure measurements reduced from an average of 141.4 mmHg to 131.9 mmHg in the intervention group, while there was an increase in the control group from 140.4 mm Hg to 142.5 mmHg. Following the Hypertension Short Message Service intervention, the difference in diastolic blood pressure in the intervention and control arm was 1.24mmHg, a reduction that was not statistically significant