Background: Nonsteroidal anti-inflammatory drugs (NSAIDs) such as Aspirin may have anticancer properties, and can be effective as a novel strategy for the treatment of colorectal cancer (CRC). The aim of this study was to assess the cytotoxic effects of Aspirin drug in CRC cell lines compared with Oxaliplatin drug in vitro. Methods: Cell viability was assessed after treatment of SW742 and SW480 cells with Aspirin and Oxaliplatin by MTT assay, and the amount of IC50 was determined. Statistical analysis was performed through one-way ANOVA and Tukey multiple range analysis (SPSS 19.0 software (P <0.05). Results: Aspirin and Oxaliplatin considerably inhibited the growth of SW742 and SW480 cell lines. SW742 cell line was more sensitive to Aspirin than SW480 cell line. The cytotoxic effect of Oxaliplatin was higher than Aspirin in both cell lines. Conclusions: This study demonstrated that both Aspirin and Oxaliplatin have cytotoxic effects on SW742 and SW480 cell lines in vitro. Thus, Aspirin may be considered as a therapeutic agent in CRC, however, further in vivo investigations are required to fully establish this effect.