Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is one of the most important and effective predators of Tetranychus spp. (Acari: Tetranychidae). This study analyzed the effects of hexythiazox and spiromesifen resistance on biological characteristics of N. californicus. Pre-oviposition, oviposition, post-oviposition times, adult lifespan, total number of eggs laid per female, net reproductive rate (R-0), intrinsic rate of increase (r(m)), doubling time (DT), mean generation time (T) and finite rate of increase (lambda) were compared among three populations: 63.9-fold hexythiazox resistant (HEX14), 53.6-fold spiromesifen resistant (SPR13) and a susceptible base population. Pre-oviposition and oviposition times, mean number of eggs/female, adult lifespan, R-0 and r(m) values were all significantly higher for the two resistant populations than for the susceptible population. Life tables of HEX14, SPR13 and the susceptible population showed that R-0 was 35.0, 26.5 and 19.4 (females/female generation), r(m) was 0.35, 0.32 and 0.30 (females/female/day), DT was 1.92, 2.07 and 2.27 days, T was 9.8, 9.8 and 9.7 days, and lambda was 1.43, 1.39 and 1.35 (individuals/female/day), respectively.