Hypertension and its complications are now responsible for about a quarter of emergency medical admissions in urban hospitals in Nigeria. It is the commonest risk factor for stroke, heart failure, chronic kidney disease, and dementia. Furthermore, high blood pressure is the commonest cause of sudden unexpected natural death in the country. Regrettably, the rate of awareness, treatment, and control is abysmally low in the country and in many parts of the world. May Measurement Month (MMM) is a global initiative of the International Society of Hypertension aimed at raising awareness of high blood pressure (BP) and to act as a temporary solution to the lack of screening programs worldwide. An opportunistic cross-sectional survey of volunteers aged ≥18 years was carried out in May 2017. Blood pressure measurement, the definition of hypertension and statistical analysis followed the standard MMM protocol. A total of 19 904 individuals with a mean age of 40.9 years, were screened during MMM17. After multiple imputation, 6709 (36.2%) had hypertension. Of individuals not receiving anti-hypertensive medication, 4140 (25.9%) were found to have hypertension. Of individuals receiving anti-hypertensive medication, 1449 (58.8%) had uncontrolled BP. MMM17 was one of the largest BP screening campaigns undertaken in Nigeria. A significant number of the participants were identified with hypertension (but not on any treatment) and uncontrolled BP despite being treated. These results suggest that opportunistic screening can identify significant numbers with raised BP.