Treatment-resistant epilepsy (TRE) is associated with low quality of life (QOL). Cannabidiol (CBD) may improve QOL, but it is unclear if such improvements are independent of improvements in seizure control. Our aim was to compare QOL at baseline and after 1 year of treatment with CBD. We hypothesized that QOL would improve independent of changes in seizure frequency (SF) or severity, mood, or adverse events. We assessed QOL using Quality of Life in Epilepsy-89 (QOLIE-89) in an open-label study of purified CBD (Epidiolex®) for the treatment of TRE. All participants received CBD, starting at 5 mg/kg/day and titrated to 50 mg/kg/day in increments of 5 mg/kg/day. We collected QOLIE-89 in adult participants at enrollment and after 1 year of treatment, or at study exit if earlier. We analyzed if the change in QOLIE-89 total score could be explained by the change in SF, seizure severity (Chalfont Seizure Severity Scale, CSSS), mood (Profile of Moods States, POMS), or adverse events (Adverse Event Profile, AEP). Associations among the variables were assessed using bivariate tests and multiple regression. Fifty-three participants completed enrollment and follow-up testing, seven at study termination. Mean QOLIE-89 total score improved from enrollment (49.4 ± 19) to follow-up (57 ± 21.3; p = .004). We also saw improvements in SF, POMS, AEP, and CSSS (all p ≤ .01). Multivariable regression results showed QOLIE-89 at follow-up associated with improvements in POMS at follow-up (p = .020), but not with AEP, CSSS, or SF (p ≥ .135). Improvement in QOL after treatment with CBD is associated with better mood but not with changes in SF, seizure severity, or AEP. Cannabidiol may have beneficial effects on QOL and mood that are independent of treatment response.