The Kenz Lifecorder EX (LC; Suzuken Co. Ltd., Nagoya, Japan) offers several potentially attractive features for researchers and practitioners compared with accelerometers such as the ActiGraph (AG; ActiGraph Health Services, Fort Walton Beach, Fla.). The purposes of this study were (i) to evaluate the LC's intra-model reliability for outputs of steps and time spent in moderate, vigorous, and combined moderate plus vigorous physical activity (MVPA) and (ii) to compare the same LC vs. AG outputs under free-living conditions. Ten participants (n = 5 males) wore two LCs and one AG accelerometer during all waking hours on one day. Steps were outputted from all monitors. Additionally, two LC and five AG intensity derivations were used to assess time in moderate activity, vigorous activity, and MVPA. Intra-class correlations (ICC) were used to assess intra-model reliability between LCs. Paired t tests and repeated-measures analyses of variance (ANOVAs) were used to assess differences between the two LCs and LC vs. AG outputs of steps and time in various intensity derivations where appropriate. No significant differences were detected between outputs from different LCs (ICCs ranged from 0.95 to 0.99). The LC detected significantly fewer steps vs. AG (mean difference = 1516 steps). All LC vs. AG vigorous-intensity derivations provided similar outputs. Additionally, comparable estimates of MVPA time were produced by one of two LC intensity derivations compared with specific AG cut points established each by Freedson, Hendelman (walking), and Matthews. LC displayed high inter-model reliability. Although the LC detected fewer steps than the AG, the LC detects time in specific PA intensity categories comparable to several existing AG cut points.