Despite the high prevalence of sleep disturbance in the heart failure population, information about its consequence on daytime function in patients with left-ventricular assist devices (LVADs) is limited. This study examined the nighttime and daytime sleep patterns and changes from pre-implant to 6 months post-implant. This study included 32 LVAD patients. Demographics, nighttime and daytime sleep variables were collected pre-implant and at 1, 3, and 6 months post-implant. Wrist actigraphy and self-report questionnaires measured objective and subjective sleep, respectively. Objective nighttime sleep data were sleep efficiency (SE), sleep latency (SL), total sleep time (TST), wake after sleep onset (WASO), and sleep fragmentation (SF). Objective daytime sleep data were nap times. Self-reported Subjective Sleep Quality Scale (SSQS) and Stanford Sleepiness Scale (SSS) were subjective measures. Increased SF and WASO scores and decreased TST and SE scores were found pre-LVAD implant, indicative of poor sleep quality. TST, SE, naptime and SSQS scores were higher at 3 and 6 months post-implant compared to baseline. Decreases in TST and SF scores were observed at 3 and 6 months post-implant along with increases in SSS scores. Increasing SSS scores and decreasing overall scores from pre- and up to 6 months post-implant suggest improvement in daytime function. This study provides information on sleep-daytime function in the LVAD patient population. Improvements in daytime sleepiness do not imply “good” sleep quality, consistent with the extant knowledge in LVAD literature. Future investigations should elucidate the mechanism by which sleep-daytime function influences quality of life.