Reduced‐sodium, added‐potassium salt substitutes have favorable effects on blood pressure, but have not been tested in India. The Salt Substitute in India Study (SSiIS) is a double‐blinded, randomized‐controlled trial designed to investigate the effects of reduced‐sodium, added‐potassium salt substitution to replace usual cooking salt use and blood pressure (BP) among hypertensive patients in rural India. The primary objective is to assess effects on systolic blood pressure at 3 months. The secondary objectives are to determine effects on diastolic blood pressure, urinary sodium, and potassium levels, and to determine acceptability of the intervention. Eligible individuals received usual salt (100% sodium chloride) or salt substitute (70% sodium chloride and 30% potassium chloride) to replace all salt required for cooking and seasoning in the household. A total of 502 participants aged ≥18 years with a history of hypertension were successfully recruited and randomized in a 1:1 ratio to intervention or control, between November 2019 and January 2020. Mean blood pressure at baseline was 133.5/83.6 mm Hg and 96% were using one or more blood pressure‐lowering medications. The overall mean average 24‐hour urinary sodium excretion was 2825 (SD, 1166) mg/L, which corresponds to a urinary salt excretion of 10.4 g/d. Baseline findings suggest sodium intake in this population significantly exceeds World Health Organization recommendations. The SSiIS trial has successfully recruited participants and is well placed to determine whether salt substitution is an effective means of lowering blood pressure for rural Indian patients with hypertension.