Background The short-message service (SMS) reminder techniques are found to be important in increasing medication adherence in non-communicable diseases. Objective To assess the effect of SMS on medication adherence in hypertension and/or type 2 diabetes mellitus. Method An observational study was conducted in the outpatient department using a semistructured questionnaire. Patients having hypertension and/or type 2 diabetes mellitus and taking at least one medication and having low to medium adherence were enrolled and short-message service was sent to them twice a week for up to two months reminding them to take medications as prescribed. At the end of two months, medication adherence was assessed using SPSS at P-value less than 0.05. Result Out of 105 patients, 64 (60.95%) were females. The mean age (±SD) was 51.15 ± 11.01 years. After two months of the short-message service reminders, majority of the patients were graded as having high adherence (73.33%) followed by medium adherence (20.0%) and low adherence (6.67%). The mean medication adherence scores on day one and after two months were 5.50 ± 1.14 and 7.50 ± 0.93 respectively (P-value=0.000). A high medication adherence was seen in individuals aged above 45 years (75.7%), males (78.0%) and those using a basic mobile phone (76.7%) after two months of follow-up; however it was statistically not significant (P-value > 0.05). Conclusion The SMS reminders had significantly improved the medication adherence in patients with hypertension and/or type 2 diabetes mellitus. However, none of the baseline variables were significantly associated with improvement in the adherence.