Prior studies of asthma in children with sickle cell disease (SCD) were based on reports of a doctor‐diagnosis of asthma with limited description of asthma features. Doctor‐diagnoses of asthma may represent asthma or wheezing unrelated to asthma. Objectives of this study were to determine if asthma characteristics are present in adults with a doctor‐diagnosis of asthma and/or wheezing, and to examine the relationship between doctor‐diagnosis of asthma, wheezing and SCD morbidity. This was an observational cohort study of 114 adults with SCD who completed respiratory symptom questionnaires and had serum IgE measurements. A subset of 79 participants completed pulmonary function testing. Survival analysis was based on a mean prospective follow‐up of 28 months and data were censored at the time of death or loss to follow‐up. Adults reporting a doctor‐diagnosis of asthma (N = 34) were more likely to have features of asthma including wheeze, eczema, family history of asthma, and an elevated IgE level (all P < 0.05). However, there was no difference in pain or ACS rate, lung function, or risk of death between adults with and without a doctor‐diagnosis of asthma. In contrast, adults who reported recurrent, severe episodes of wheezing (N = 34), regardless of asthma, had twice the rates of pain and ACS, decreased lung function and increased risk of death compared with adults without recurrent, severe wheezing. Asthma features were not associated with recurrent, severe wheezing. Our data suggest that wheezing in SCD may occur independently of asthma and is a marker of disease severity. Am. J. Hematol. 2011. © 2011 Wiley‐Liss, Inc.