Cyantraniliprole has been widely used in China for controlling many pests, including the small brown planthopper (SBPH) Laodelphax striatellus (Fallén), which is a major pest of rice. Sublethal effects of cyantraniliprole on SBPH have not yet been examined. In this study, 3rd instar nymphs of SBPH were exposed to the LC₁₀, LC₂₀, and LC₃₀ (3.17, 6.07, and 9.70 mg/L) of cyantraniliprole, which led to reductions in survival rate and hatchability of the F₀ generation. Compared with the control, sublethal concentrations of cyantraniliprole significantly prolonged the development time of the 4th and 5th instar nymphs of the F₁ generation. In the LC₁₀, LC₂₀, and LC₃₀ treatment groups, the nymphal duration was prolonged by 1.98, 0.99, and 2.54 d, respectively. In addition, the sublethal concentrations of cyantraniliprole shortened the adult preoviposition period. The activities of cytochrome P450 monooxygenases and carboxylesterase in SBPH were promoted after treatment with sublethal concentrations of cyantraniliprole. The increase in insecticide resistance may be due to the increase in the activity of detoxification enzymes. Therefore, this research can provide a theoretical reference for the treatment of resistant SBPH.