Background: The tumor suppressor in lung cancer-1 (TSLC1) is a tumor-suppressor gene. We evaluated the correlation between TSLC1 expression and clinicopathological characteristics of colorectal cancer patients by comparing primary colorectal cancer and adjacent normal colorectal tissues. Methods: TSLC1 expression was evaluated in 100 pairs of primary colorectal cancerous and corresponding normal colorectal tissues using immunohistochemical staining on paraffin-embedded sections. The correlation between immunohistochemical findings and clinicopathological factors was then investigated. Age, gender, and clinicopathological presentation of patients were also noted. Results: TSLC1 was expressed in all tissues. A 71%- down regulation of TSLC1 was colorectal cancer specimens compared to the matched normal tissues. There were statistically significant correlations between TSLC1 expression and stage, location, and lymph node metastasis. Conclusion: TSLC1 expression may be a favorable biologic marker and a useful prognostic indicator in patients with colorectal cancer. Keywords: TSLC1, Colorectal cancer, Tumor suppressor gene, Immunohistochemistry