This study was designed to compare the chemical compositions and effect of essential oils from the peels and seeds of sweet orange on cholinergic (acetylcholinesterase [AChE], butyrylcholinesterase [BChE]) and monoaminergic (monoamine oxidase [MAO]) enzymes. The ability of the essential oils to protect the brain against Fe2+‐induced lipid peroxidation was also investigated. Forty and forty‐four compounds were identified in peels and seed essential oils, respectively, using gas chromatography. The essential oils inhibited AChE, BChE and MAO in dose‐dependent manner. However, essential oil from the peels had higher inhibition on cholinergic enzymes but lower inhibitory effect on MAO and Fe2+‐induced lipid peroxidation compared to the seed essential oils. This study also revealed the presence of volatile compounds. Conclusively, both essential oils could be used as therapeutic agents in the management of Alzheimer's disease. Practical Applications Sweet orange (Citrus sinensis) peels and seeds are waste materials in the production of orange juice and can be used as a source to produce essential oils which can be of use in the production of functional foods and nutraceuticals. This study provided reference information for the first time on the chemical composition and potential application of sweet orange peels and seed essential oils in the treatment and management of Alzheimer's diseases.