Individuals with sickle cell disease (SCD) experience neurocognitive decline, low medication adherence, increased unemployment, and difficulty with instrumental activities of daily living (IADL). The relationship between self-perceived cognitive difficulties and IADLs, including employment, school enrollment, independence, engagement in leisure activities, and medication adherence is unknown. We hypothesized that self-reported difficulties across neurocognitive areas would predict lower IADL skills. Adolescent and adult participants of the multi-site Sickle Cell Disease Implementation Consortium (SCDIC) (n = 2436) completed patient-reported outcome (PRO) measures of attention, executive functioning, processing speed, learning, and comprehension. Cognitive symptoms were analyzed as predictors in multivariable modeling. Outcome variables included 1) an IADL composite that consisted of employment, participation in school, reliance on others, and leisure pursuits, and 2) hydroxyurea adherence. Participants reported cognitive difficulty across areas of attention (55%), executive functioning (51%), processing speed (57%), and reading comprehension (65%). Executive dysfunction (p < 0.001) and sometimes or often experiencing learning difficulties (p < 0.001 and p = 0.04) and poor comprehension (p = 0.000 and p = 0.001), controlled for age (p < 0.001), pain (p < 0.001), and hydroxyurea use (p = 0.001), were associated with poor IADL skills. Executive functioning difficulties (p = 0.021), controlled for age (p = 0.013 for ages 25–34), genotype (p = 0.001), and hemoglobin (p = 0.004), predicted hydroxyurea non-adherence. Analysis of PRO measures indicated that cognitive dysfunction is prevalent in adolescents and adults with SCD. Cognitive dysfunction translated into clinically meaningful outcomes. PRO of cognitive symptoms can be used as an important adjunct clinical tool to monitor symptoms that impact functional skills, including engagement in societal activities and medication adherence.