AbstractThe diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), has evolved resistance to various types of insecticides in the field. In the present study, the resistance of P. xylostella (designated Cya‐SEL) to cyantraniliprole increased to 30.6 and 326‐fold after 26 generations of selection, compared with the field population (TA) and susceptible population (LAB), respectively. The resistant population also had developed low to moderate levels of resistance to abamectin (3.3‐fold), flubendiamide (14.1‐fold), and chlorantraniliprole (24.3‐fold). Synergism tests indicated that piperonyl butoxide (PBO) and diethyl maleate (DEM) increased the toxicity of cyantraniliprole in the selected strain, i.e., synergism ratio was 2.8 and 3.3‐fold, respectively. Reciprocal crosses were made between the susceptible (LAB) and resistant strain collected from Zengcheng (ZC). The degree of dominance and overlapping confidence intervals of LC50 values of F1 progenies (ZC♀ × LAB♂ and LAB♀ × ZC♂) suggested an autosomal and incompletely recessive mode of resistance to cyantraniliprole. The test of monogenic inheritance based on a backcross of F1 progeny with the ZC population indicated that resistance to cyantraniliprole was controlled by multiple genes. Additionally, Cya‐SEL had a lower reproductive ability and relative fitness than the other tested populations. These findings provide useful information for effective resistance management strategies against P. xylostella.