The dissipation behaviour and left-over residues of Hexaconazole fungicide and Lambda-Cyhalothrin pesticide in potato plant and soil were analysed by gas chromatography mass spectrometry (GC-MS). At fortified levels of 10, 100 and 500 μg/kg, the recoveries of Lambda-Cyhalothrin and Hexaconazole were in the range 81.66–93.25% and 76.11–93.92% with standard deviations of 0.87–8.13% and 0.88–7.68%, respectively. The half-life ranges for all matrices (tuber, stem, leaf and soil) were 13.8–17.3 days for Hexaconazole and 11.5–17.3 days for Lambda-Cyhalothrin. The final concentration of Hexaconazole and Lambda-Cyhalothrin in tuber at harvest was compared with the maximum residual limit (MRL) of CODEX (0.01 mg/kg) and EU (0.02 mg/kg) and found to be higher at dosages of 30 g/ha and 40 g/ha, respectively. There was no residual concentration of either pesticide in the control plot. The results obtained from risk evaluation showed that the risk of Lambda-Cyhalothrin at dosage of 7–15 g/ha and Hexaconazole at dosage of 5–30 g/ha was negligible to humans while a dose of 40 g/ha for Lambda-Cyhalothrin resulted in a health hazard to humans. This study may prove helpful in ascertaining the MRL and also provide direction on the appropriate use of Lambda-Cyhalothrin and Hexaconazole in potato farming as the waiting period from last application to harvest is 25 days for Hexaconazole and 38 days for Lambda-Cyhalothrin.