Abstract Background More than half of the individuals with hypertension remain undiagnosed in India. The National Non-Communicable Disease (NCD) program has implemented opportunistic screening to improve diagnoses. In the public health facilities across 18 districts in nine states of India, we estimated the missed opportunity for hypertension detection in routine program settings. Methods In each of the chosen districts, we conducted a cross-sectional study in one district hospital (DH), one community health centre (CHC), and three primary health centres (PHCs), selected randomly. We collected data from 706 consecutively enrolled eligible out-patient department (OPD) attendees in each facility type and abstracted the data regarding coverage and yield of opportunistic screening for hypertension from the available registers. We then derived the missed opportunity for hypertension detection. We also estimated the median time for Blood Pressure (BP) measurement through observation and derived the staff requirement for BP screening at each facility type. Results Of the 41,012 eligible OPD attendees, 32.1% [31.6%-32.5%]) were screened for hypertension. The yield for hypertension screening was 23.2% (3,050/13,157). Among the OPD attendees, the proportion of missed diagnoses for hypertension among the expected was 57.1% (1,962/3,437), 67.4% (1,860/2,758), and 79.3% (2,597/3,274) in PHCs, CHCs, and DHs, respectively. The minimum number of dedicated staff required for measuring BP was one at PHC/CHC and two at DH. Conclusions Sixteen out of every 100 eligible OPD attendees miss the opportunity to get diagnosed with hypertension due to inadequate screening coverage. Innovative measures like task-sharing and utilizing trainee nurses for BP measurement to overcome staff shortages can help improve screening coverage.