Changes in nitrite contents and antioxidant properties of cowpeas processed by three cooking methods (boiling, steaming and frying) during 4 ℃ storage were investigated. The polyphenol content and antioxidant activity of extracts from different treated cowpeas were determined by Folin-Ciocalteu assay and TEAC assay, respectively. Results showed that the different cooked cowpeas had significantly higher nitrite contents than the raw cowpeas. The nitrite contents in all the samples increased at first and then decreased during storage, with the highest contents being obtained at 3 days of storage. The boiled cowpeas had significantly higher nitrite content than the other processed cowpeas throughout the storage. The free phenolics content was significantly decreased in cooking processed cowpeas. Steamed cowpea showed the highest phenolics content, whereas fried cowpea had the lowest. Increases in bound phenolics content were observed after steaming and frying, whereas a decease was noted after boiling. During storage, the free phenolics content in cooked cowpeas increased at first and then decreased with the extension of storage time, while the bound phenolics content significantly reduced. Similar trend was observed in total antioxidant activity. A high correlation was observed between the total antioxidant activity and the polyphenol content.