The present study was carried out to investigate the changes in fatty acid composition and their key fatty acid ratio on mixing of canola oil (CLO) with cold pressed stinging nettle (SNO) oil during heating at constant temperature of 180 o C for 10 hours (h). The blended oils were prepared by gravimetrically mixing of CLO and SNO at various ratios of 60:40 and 40:60w/w, respectively. The fatty acid composition and key fatty acid ratio were analyzed by Gas chromatography-mass spectrometry (GC-MS). Trans fatty acid in fresh CLO and SNO oils of 1.1 and 0.05%, whereas fresh blended oils of CLO: SNO (40:60, 60:40 w/w) contained 0.44, 0.91% and heated oils of CLO, SNO and CLO: SNO (40:60, 60:40 w/w) were found in the range from 1.35-2.49%, 0.06-0.09% and 0.46-0.51%, 1.02-1.27% trans fatty acids, correspondingly. The linolenic fatty acid is prone to more oxidation in heated oils, the percentage of linolenic acid contained in fresh CLO, SNO and blended (40:60, 60:40) CLO: SNO oil samples of 10.58, 0.00% and 3.94, 6.64%, respectively. The heated oils included linolenic acid, decreased from the Downloaded by [Thammasat University Libraries] at 03:A c c e p t e d M a n u s c r i p t 2 range of 10.27-6.54%, 0.00, and 3.93-3. 79%, SNO, and CLO: SNO (40:60, 60:40 w/w), respectively. The oxidation parameters were also analyzed such as free fatty acids, peroxide value, iodine value, conjugated diene and triene using standard official methods. The best results of FFAs, PV were obtained in blended CLO: SNO (40:60 w/w) oil at 0.31%, 0.63meqO 2 /Kg of oil, respectively. The mean values of IV, CD and CT were obtained in blended CLO: SNO (40:60 w/w) oil at 0.79%, 60% and 31.36%, respectively during 10h heating. The obtained results show that mixing of CLO with SNO (Urtica dioica L.) increased the stability against oxidation and consequently enhanced the worth of CLO during heating/frying route.