Greater phosphorus intake has been associated with lower levels of blood pressure in cross-sectional studies. This association, however, has not been assessed prospectively. We studied 13444 participants from the Atherosclerosis Risk in Communities cohort and the Multi-Ethnic Study of Atherosclerosis, with diet assessed at baseline using validated food frequency questionnaires. Blood pressure and use of antihypertensive medication were determined at baseline and during follow-up visits. Compared to individuals in the lowest quintile of phosphorus intake at baseline, those in the highest quintile had lower baseline systolic and diastolic blood pressure after adjustment for dietary and non-dietary confounders (−2.0 mmHg, 95% confidence interval −3.6, −0.5; p for trend=0.01; and −0.6, 95% confidence interval −1.6, +0.3, p for trend=0.20, respectively). During an average 6.2 years of follow-up, 3345 cases of hypertension were identified. Phosphorus intake was associated with the risk of hypertension (hazard ratio 0.80, 95% confidence interval 0.80-1.00, comparing extreme quintiles; p for trend=0.02) after adjustment for non-dietary factors, but not after additional adjustment for dietary variables (hazard ratio 1.01, 95% confidence interval 0.82-1.23, p for trend=0.88). Phosphorus from dairy products but not from other sources was associated with lower baseline blood pressure and reduced risk of incident hypertension. Hazard ratios (95% confidence interval) comparing extreme quintiles were 0.86 (0.76-0.97), p for trend=0.01, for phosphorus from dairy foods and 1.04 (0.93-1.17), p for trend=0.48, for phosphorus from other foods. These findings could indicate an effect of phosphorus in conjunction with other dairy constituents or of dairy itself without involvement of phosphorus.