May Measurement Month 2021 (MMM21) is the fourth edition of the global initiative in Poland initiated by the International Society of Hypertension (ISH) and aimed at raising awareness of hypertension and the need for blood pressure (BP) screening. An opportunistic cross-sectional survey of volunteers aged ≥18 was carried out in 132 sites - between May and September 2021. Blood pressure was measured in 1699 subjects (mean age: 40.8 ± 17.0 years; 68.8% females). After multiple imputation, the age and sex standardized systolic and diastolic BP was 126.6/78.7 mmHg for the entire group, 133.8/81.9 mmHg in individuals on antihypertensive medication, and 125.4/78.6 mmHg in those not taking antihypertensive drugs. The proportion of subjects with high BP (≥140/90 mmHg) were: 30.9% for the entire group, 40.4% in subjects taking antihypertensive drugs, and 17.9% in those not taking antihypertensive drugs. Of all participants, 33.9% were in the age range of 18-29 years and we observed higher BP levels and more frequent BP elevation in males in this age group. These data provide unique insights into the hypertension rates during the COVID-19 pandemic. Due to the associated restrictions, only limited data could be obtained for older adults. Interestingly, among young Polish participants, the rate of hypertension and the level of BP were higher in males compared to females, suggestive perhaps of a higher susceptibility of males to experience a rise in BP during specific circumstances associated with a pandemic.