This study examined the relationship between job security and organizational citizenship behaviour in Deposit Money Banks in Rivers State. The study adopted a cross-sectional research survey design. Primary source was generated through self- administered questionnaire. The population of the study was 202 employees of 21 Deposit Money Banks in Port Harcourt. The sample size of 134 was determined using the Taro Yamane’s formula for sample size determination. The reliability of the instrument was achieved by the use of the Cronbach Alpha coefficient with all the items scoring above 0.70 to be selected. Data generated was analyzed and presented using both descriptive and inferential statistical techniques. The hypotheses were tested using the Spearman’s Rank Order Correlation Statistics. The finding revealed that there is a significant relationship between job security and organizational citizenship behaviour in Deposit Money Banks in Rivers State. The study thus concludes that job security significantly influences organizational citizenship behaviour in Deposit Money Banks in Rivers State. The study recommends that Deposit Money Banks should strive to provide job security to their employees as it has a positive and significant impact on organizational citizenship behaviour.