The study results revealed variations in the toxicity of flaxseed, rosemary, and sage oils on the larvae and adults of the Colorado potato beetle Leptinotarsa decemlineata. Rosemary oil and flaxseed oil demonstrated higher toxicity against the larvae compared to sage oil, with average mortality rates of 22.22%, 19.44%, and 14.44%, respectively. The results indicated that the average mortality rate of the larvae increased proportionally with higher oil concentrations (2%, 4%, 6%, and 8%), reaching 10.00%, 14.07%, 17.03%, and 33.70%, respectively. Additionally, the study showed that the average mortality rate of the larvae increased cumulatively with longer exposure periods 24, 48, and 72 h, recording 8.06%, 17.78%, and 30.28%, respectively. Furthermore, the study highlighted the superior toxicity of flaxseed oil against adult Colorado potato beetles compared to rosemary and sage oils, with average mortality rates of 15.27%, 3.88%, and 1.94%, respectively. The concentrations of the oils used in the study had a significant effect on increasing the average mortality rates, which were 2.22%, 3.33%, 8.51%, and 14.07% as the concentrations increased. The results also demonstrated that the cumulative post-exposure period led to a noticeable increase in the average mortality rate of adult beetles, reaching 2.77%, 8.61%, and 9.72%, respectively.