Citrus by-products are a major source of phenolic compounds which could serve as natural antioxidants. This study was carried out to determine the free radical scavenging potential and the phenolic content of the aqueous-ethanol extract of the seeds of Citrus sinensis. Preliminary phytochemical screening of the crude extract was also investigated to find out the different secondary metabolites present. The seeds of C. sinensis were obtained from local source, dried and pulverized using mechanical grinder. The resulting powder was subsequently extracted by cold maceration in 70% ethanol. Preliminary phytochemical screening was carried out employing standard procedures. Free radical scavenging and phenolic content was determined, utilizing DPPH and Folin-ciocalteu’s phenolic reagent respectively. Phytochemical screening revealed the presence of tannins, carbohydrates, alkaloids, flavonoids, cardiac glycosides and steroids. The per cent free radical scavenging activity of the extract was found to be 89.30%, with IC50 of 0.136 mg/mL. The standard substance (ascorbic acid) gave 86.66% inhibition of the DPPH radical activity, with IC50 of 0.332 mg/mL. The total phenolic content of the extract expressed as gallic acid equivalent was 8.54 mg/g of dry mass at 1mg/mL concentration. There was a positive correlation between radical scavenging activity and phenolic content of the extract. The high free radical scavenging activity demonstrated by the aqueous-ethanol extract of the seeds of C. sinensis is traceable to the copious amount of total phenol found in the extract. There is need for further phytochemical study in order to isolate the particular compounds that could be responsible for this activity.