Introduction Capsicum grown in low-cost polyhouses (a protective shade made up of polythene used for growing high-value agricultural products) is often infested by thrips and acephate is an insecticide, which is frequently and repeatedly used for controlling this pest. Objectives Since a polyhouse microclimate is different from that of an open field, a study was carried out to compare the decline pattern of acephate residues in capsicum grown in polyhouse to that grown in open field. Methods Laboratory standardized methodologies using gas liquid chromatography was adopted to estimate residues of acephate and its metabolite, methamidophos in capsicum fruits. Results and Conclusion Higher initial residues (0.39 ppm) and persistence of acephate (pre-harvest interval = 16 days) and its methamidophos metabolite was detected in capsicum grown in polyhouse as compared to that grown in open field (pre-harvest interval = 12 days) in spite of higher rate of growth and consequent residue 'dilution' in polyhousegrown capsicum.