Purpose: This study was aimed to compare and evaluate the fatigue resistance and the color stability of polyoxymethylene (Acetal) and Bre-Flex (2nd edition). Materials and Method: Twenty partially edentulous models Kennedy class I were constructed with first premolars are last abutments. Models were divided into two equal groups Group A: Construction of RPD with Polyoxymethylene (Acetal) clasps and denture base, Group B: Construction of RPD with Polyamide (Bre-flex 2nd edition) clasps and denture base. The Retention and fatigue resistance of each clasp after cycling intervals (360 cycles, 720 cycles, 1440 cycles, and 2880 cycles) were measured by applying withdrawal force to it using a universal testing machine. The data of the retentive force magnitudes at different intervals were collected and tabulated. Also, the color change was evaluated after 4 weeks by measured a total 20 specimens for each group (size of the disc was set to 4 mm) in different immersion media cola (acidic pH), Licorice (alkaline pH), (neutral pH) Distilled Water using a portable Reflective spectrophotometer. The data were subjected to statistical analysis using 3-way-ANOVA test, Student's t and paired t-tests. Results: Regarding the retention and fatigue resistance it was found that group B recorded statistically significant higher mean value than group A. Regarding the color change the total effect of the main group on color change (ΔE); it was found that group A recorded statistically significant higher change mean value than group B as revealed by two-way ANOVA test (p=<0.0001<0.05). Conclusion: The removable partial dentures were constructed the denture bases and the clasps with the poly amid Bre-flex 2nd edition was exhibited superior color stability and fatigue resistance when compared with the removable partial dentures constructed their claps and denture bases from polyoxymethylene (Acetal).