Pomacea canaliculata is a freshwater snail native to South America that has become a serious pest of rice crops. Insecticides are used to control other pests in paddy fields and P. canaliculata is collaterally exposed. Here a P. canaliculata population from a rice field (RF) where the insecticides bifenthrin and imidacloprid (IMC) were applied was compared with a reference site (RS). The activities of three metabolic endpoints, namely acetylcholinesterase (AChE), carboxylesterase (CbE) and glutathione-S-transferase (GST) were measured to test metabolic stress. Intestine and midgut-gland of snails after 7 and 30 days of insecticide application were studied. A possible effect of IMC on shell thickness was also explored. The results indicate an inhibition of CbE and GST activities in the intestine of RF snails relative to RS snails at 7 days, while AChE and GST increased in the intestine after 30 days of IMC exposure. GST in the midgut-gland of RF snails was inhibited with respect to RS snails at 7 and 30 days, whereas CbE increased at 30 days in RF snails. Thinner shells with lower proportion of ash content were observed in snails from RF. Exposure to pesticides exerts neurotoxic resistance and oxidative stress in P. canaliculata and is probably responsible for the alteration in the shell development.