Actigraphy has become a common method of measuring sleep due to its non-invasive, cost-effective nature. An actigraph (Readiband™) that utilizes automatic scoring algorithms has been used in the research, but is yet to be evaluated for its inter-device reliability. A total of 77 nights of sleep data from 11 healthy adult participants was collected while participants were concomitantly wearing two Readiband™ actigraphs attached together (ACT1 and ACT2). Sleep indices including total sleep time (TST), sleep latency (SL), sleep efficiency (SE%), wake after sleep onset (WASO), total time in bed (TTB), wake episodes per night (WE), sleep onset variance (SOV) and wake variance (WV) were assessed between the two devices using mean differences, 95% levels of agreement, intraclass correlation coefficients (ICC), typical error of measurement (TEM) and coefficient of variation (CV%) analysis. There were no significant differences between devices for any of the measured sleep variables (p>0.05). TST, SE, SL, TTB, SOV and WV all resulted in very high ICC's (>0.90), with WASO and WE resulting in high ICC's between devices (0.85 and 0.80, respectively). Mean differences of −2.1 and 0.2 min for TST and SL were associated with a low TEM between devices (9.5 and 3.8 min, respectively). SE resulted in a 0.3% mean difference between devices. The Readiband™ is a reliable tool for researchers using multiple devices of this brand in sleep studies to assess basic measures of sleep quality and quantity in healthy adult populations.