ABSTRACT: Among ethnic minority groups in Europe, blood pressure (BP) control is often suboptimal. We aimed to identify determinants of suboptimal BP control in a multi-ethnic population. We analyzed cross-sectional data of the Healthy Life in an Urban Setting (HELIUS) study, including 3571 participants aged 18-70 with prescribed antihypertensive medication, of various ethnic backgrounds (500 Dutch, 1052 African Surinamese, 656 South-Asian Surinamese, 637 Ghanaian, 433 Turkish, and 293 Moroccan) living in Amsterdam, the Netherlands. 53.3% of the population had suboptimal BP control, defined as BP ≥140/90 mmHg despite prescribed antihypertensives. Using multivariate logistic regression analysis, female sex (OR 0.50, 95%CI 0.43-0.59), being married (0.83, 0.72-0.96), smoking (0.78, 0.65-0.94), alcohol intake (0.80, 0.66-0.96), obesity (1.67, 1.35-2.06), cardiovascular disease (CVD) history (0.56, 0.46-0.68), non-adherence to antihypertensives (1.26, 1.00-1.58), and family history of hypertension (1.19, 1.02-1.38) were identified to be independently associated with suboptimal BP control in the total population. In the ethnic-stratified analysis, factors associated with better BP control were female sex (all ethnic groups), smoking (Turks), and CVD history (Dutch, South-Asian Surinamese, and African Surinamese), whereas factors associated with suboptimal BP control were older age (Turks), obesity (Dutch, African Surinamese, Ghanaian, and Turks), and non-adherence to antihypertensives (Dutch). In conclusion, our analysis identifies several key determinants that are independently associated with suboptimal BP control in a multi-ethnic population, with some important variations between ethnic groups. Targeting these determinants may help to improve BP control.