Although pulmonary hypertension (PHT) is a common complication in patients with sickle cell disease (SCD), the rate of development of PHT and the factors that affect disease progression are unknown. We observed 93 patients over a median follow‐up period of 2·6 years (range 0·2–5·1 years). Data were censored at the time of death or loss to follow‐up. Pulmonary hypertension was associated with an increased risk of death (relative risk, 9·24; 95% confidence interval: 1·2–73·3; P = 0·01). There was no difference in the risk of death when patients with different degrees of PHT were compared. Lactate dehydrogenase and blood urea nitrogen were significantly associated with PHT in a logistic regression model. Higher levels of fetal haemoglobin and treatment with hydroxycarbamide were observed more frequently in patients without PHT. Thirteen per cent of patients with no previous evidence of PHT developed PHT following 3 years of observation. In conclusion: (1) PHT, regardless of severity, is associated with an increased risk of death in SCD patients; (2) haemolysis is strongly associated with PHT in SCD; (3) high levels of fetal haemoglobin and hydroxycarbamide therapy may decrease the occurrence of PHT; (4) screening for PHT is indicated for SCD patients in their non‐crisis, steady states.