Hypertension control rates are low in sub-Saharan Africa. Population-specific determinants of blood pressure (BP) control have not been adequately described. We measured BP and conducted interviews to determine factors associated with BP control among adults attending a hypertension clinic in Tanzania. Three hundred adults were enrolled. BP was controlled in 47.7% at the study visit but only 28.3% over 3 consecutive visits. Demographic and socioeconomic factors were not associated with control. Obesity and higher medication cost were associated with decreased control. Their effect was mediated through adherence. Good knowledge of (OR=2.5, 95%CI=1.0–6.1, p=0.047), attitudes towards (OR=2.7, 95%CI=1.0–7.1, p=0.04) and practices concerning (OR=5.4, 95%CI=2.3–13.0, p<0.001) hypertension were independently associated with increased control, even after adjusting for mediation through adherence. Good adherence had the strongest association with control (OR=14.6,95% CI=5.8–37.0, p<0.001). Strategies to reduce hypertension-related morbidity and mortality in sub-Saharan Africa should target these factors. Interventional studies of such strategies are needed.