This work, entitled ATM Service Quality and Customer Satisfaction: a Study of First Bank Nigeria Plc and Union Bank Nigeria Plc aims at operating the major constructs: service quality and customer satisfaction; and unveiling the relationship between the independent variable, service quality (made up of reliability, assurance, tangibles, empathy, responsiveness and cost) and dependent variable, customer satisfaction (made up of referral and repeat use) to be able to project the most prominent of these independent variables that banks should seriously improve on to ultimately increase customer satisfaction. Being an empirical study, the researcher made use of primary use of primary data. Questionnaires were administered on 503 users of ATMs spread across the three senatorial zones of Delta State. A five point Likert scale comprising 37 positive statements covering the variables under study was used. The reliability of the instrument was determined using Cronbach’s Alpha and the value is 0.830. This shows a high degree of internal consistency of the measuring instrument used. Fourteen hypotheses tested reveal that there are correlations between the dependent and independent variables. The study reveals that reliability, assurance, responsiveness and cost were significant but tangibles and empathy were not significant at least at 5 percent significance level when regressed with referral. Similarly, a regression of the six independent variables (Reliability, Assurance, Tangibles, Empathy, Responsiveness and Cost) and Repeat-Use (another dependent variable) shows that the constant, reliability, responsiveness and cost were significant but assurance, tangibles and empathy were not significant at least at 5 percent significance level. This indicates that reliability, cost and assurance have great effect on both repeat use and referral, hence should not be neglected. The study further reveals that there is no serious problem of multi-collinearity among the independent variables of the study. This implies that each of these variables can stand on their own, validating the acronym, RATERC, used in this study. Finally, the paper recommends that banks should remove the charges attached to the use of ATMs; stop issuing out currencies in bits as a ploy to deduct #65 from customer’s account for each withdrawal made; adhere to the CBN policy on the use of other banks ATM cards on own machines, among others.