Objective: To investigate and compare the retention rates of Flowable-Nanocluster-Composite and Resinmodified-Glass-Ionomers in non-carious cervical lesions in maxillary molars. Study Design: Prospective cross-sectional comparative study. Place and Duration of Study: Department of Operative Dentistry, Armed Forces Institute of Dentistry, Rawalpindi, from Jan 2017 to Dec 2018. Methodology: Male patients ranging from 30-40 years with moderate non-carious cervical lesions of maxillary premolars and molars of either quadrant presenting to out-patient department were selected through convenience sampling. These lesions were restored with Flowable-Nanocluster-Composite and Resin-Modified-GlassIonomer. Retention of these two materials over the period of 6 months, 1 year and 2 years was noted. Chi square statistics were used to compare groups. Results: The retention of Flowable-Nanocluster-Composite was 92% in 6 months, 85% in one year and 81% in two years. Whereas, for resin-modified-glass-ionomer restorations, the frequency of retention of the filling material was 97% at 6 months, 93% at one year and 89% at two years period. Out of the total 74 resin-modified-glassionomers restorations, 8 (11%) had dislodged by the end of the second year as compared to 14 (19%) dislodged restorations for Flowable-Nanocluster-Composite. Conclusion: In conclusion, the study reveals that resin modified glass-ionomer has a superior retention rate over the period of two years as compared to Flowable-Nanocluster Composite. A dentist should have an insight into compositions of restorative materials for the longevity of their retention in various lesions.