The effects of some processing and extraction techniques on the tannin content and antioxidant activities of Sorghum bicolor (Linn) were evaluated. The ethanolic, methanolic and water extracts from the sorghum seeds were assessed after being fermented, or oven-dried for 0 (OVD-0), 30 (OVD-30) and 60 (OVD-60) mins, along with those of the chaff collected after fermentation, and the unprocessed sorghum (control). Tannin, total flavonoids, total phenol, polyphenol contents and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging analysis were determined. All the processing techniques combined with the extraction methods significantly reduced (p<0.05) the tannins. OVD-30 combined with methanol extraction, and all the oven-drying techniques combined with aqueous extraction significantly increased (p<0.05) the flavonoids contents. Flavonoids levels in other methanol extracts and the ethanol extracts of sorghum seeds subjected to oven-drying methods were reduced significantly (p<0.05). The amount of phenolic extracted with both ethanol and methanol significantly increased (p>0.05) during the period of oven-drying. The phenolic contents in the seeds were reduced significantly (p<0.05) when extracted with an aqueous solution. The amount of polyphenols was increased significantly (p<0.05) by ethanol extraction when treated with air-drying (OVD-0). The DPPH scavenging activity was increased significantly (p<0.05) by the processing methods when subjected to either aqueous or methanolic extraction. Fermentation and oven-drying are a highly effective method of reducing the anti-nutritional factors of sorghum. Therefore, the therapeutic values of the processed sorghum seeds may be improved during consumption.