Chlorantraniliprole (CAP) is a novel amide insecticide widely used in agriculture. Trace residues of CAP in the environment pose a threat to the development and metamorphosis of the silkworm (Bombyx mori). However, the mechanisms by which CAP exposure disrupts insect metamorphosis remain poorly understood. This study investigated the levels of intracellular Ca²⁺ and 20-hydroxyecdysone (20E) following exposure to low concentrations of CAP. The results revealed that CAP exposure both directly caused increased Ca²⁺ levels and indirectly promoted an increase in Ca²⁺ levels by inducing an elevation in 20E levels. Furthermore, increased Ca²⁺ levels inhibited the expression of Ftz-f1, leading to abnormal pupation. Our study reveals for the first time the sublethal effects of CAP mediated by the Ca²⁺-Ftz-f1 axis. The findings herein provide a reference for evaluating the safety of environmental residues of amide pesticides on insects.