Elevated blood pressure (BP) is a growing burden worldwide, leading to over 10 million deaths each year. May Measurement Month (MMM) is a global initiative of the International Society of Hypertension (ISH) aimed at raising awareness of high BP and acting as a temporary solution to the lack of screening programmes worldwide. As part of MMM, screening in South Africa in 2017 revealed that 24.5% of adults (mean age = 31 years) have hypertension and only half of those with hypertension had controlled BP. These data highlight the need for continued screening and awareness campaigns. An opportunistic cross-sectional survey of volunteers aged ≥18 years was carried out in May 2018. Blood pressure measurements, the definition of hypertension and statistical analyses followed the MMM protocol. The sites screened were general populations and university campuses in preference to hospitals and clinics, aiming to raise awareness and allow access to screening to those less likely to be aware of their BP. In total, 2965 individuals (age 40.5 ± 18.2 years) were screened. After multiple imputation for missing BP readings, 34.6% had hypertension, only 56.7% of those with hypertension were aware, 21.2% of those not receiving treatment for hypertension were hypertensive, and a large proportion (42.5%) of individuals receiving antihypertensive medication had uncontrolled BP. These results suggest that opportunistic screening campaigns can identify significant numbers with undiagnosed and uncontrolled hypertension. The high proportions of individuals with undiagnosed and treated uncontrolled hypertension highlight the need for hypertension awareness campaigns and more rigorous management of hypertension.