Background: This study aimed to assess the effect of aging of composite tube on color change of composite resins. Materials and Methods: This in vitro, experimental study evaluated Enamel and Dentin composite types of 3M-Z350XT, Bisco-Aelite-aesthetic and GC-Essentia. Composite discs (n=6) measuring 1 x 8 mm were fabricated using newly opened composite tubes. The color of composite discs was measured by Easy Shade spectrophotometer according to the CIELab color space. Next, the composite tubes underwent accelerated aging according to the Arrhenius model and were incubated at 37°C in dry environment for 12 weeks. Composite discs with the same dimensions were fabricated again and their color was measured as before. Data were analyzed using SPSS. Results: The change in a* and b* parameters was significant in all groups except for the Z350XT-Enamel (P=0.15). In the a* axis, the color of Aelite-Enamel shifted to green and the color of Aelite-Dentin, Essentia-Enamel, Essentia-Dentin and Z350XT-Dentin shifted to red. In the b* axis, the color of Z350XT-Dentin, Essentia-Enamel, Essentia-Dentin and Aelite-Dentin shifted to blue while the color of Aelite-Enamel shifted to yellow. In the L* axis, the changes in Aelite-Dentin, Aelite-Enamel and Essentia-Enamel were not significant but the changes in other composites were significant. The L* parameter increased in these three groups and they became lighter. Conclusions: Aging of composite tube affects the color change of composite resins; thus, care must be taken when using aged composite tubes.