The purpose of this study is to determine the level of job satisfaction of Registered nurses in Muscat and relationships to Herzberg's motivation and hygiene factors. The theoretical underpinning of this study is based on Herzberg's concepts, in which an individual's motivation and hygiene factors are met within an organization, to the extent that the individual employee will express in job satisfaction. A descriptive, nonexperimental research design was used. The Work Quality Index and a demographic survey were given to 202 registered nurses at Sultan Qaboos University Hospital (SQUH) and Royal Hospital (RH) in Muscat. The data was collected over three weeks and was analyzed, using descriptive statistic, t-test, ANOVA for independent mean, and correlation statistics as appropriate. The results indicate that nurses in the two hospitals had a moderate level of job satisfaction. It also proves that motivation factors and hygiene factors are significantly correlated with job satisfaction, meaning that the fulfillment of both types of factors determines the overall job satisfaction of the nurses.