Introduction. The aim of this prospective study was to investigate excessive daytime sleepiness (EDS) over time and in relation to other PD symptoms among people with Parkinson's disease (PD). Methods. Thirty participants younger than 65 years with PD were randomly selected. At inclusion, mean (SD) disease duration was 6.2 (4.8) years and median (min-max) severity of PD was classified as stage II (stages I-III) according to Hoehn and Yahr. Participants were followed annually for 10 years with clinical assessments of their PD status, medications, comorbidities, and a standardized interview about their sleep habits and occurrence of daytime sleepiness. EDS was assessed by the self-reported Epworth Sleepiness Scale (ESS). Seventeen participants completed the 10-year longitudinal follow-up. Results. Fifteen of 30 persons were classified to suffer from EDS (ESS > 10) at baseline. At the group level, EDS remained stable over 10 years and did not deteriorate in parallel with worsening of motor symptoms. Furthermore, EDS was associated with sleep quality, fatigue, anxiety, depression, and axial/postural/gait impairments. Conclusions. EDS did not worsen over 10 years, although other PD aspects did. EDS in PD seems to be a complex nonmotor symptom that is unrelated to deterioration of motor symptoms in PD.