Objective To detect the methylation status of DLEC1 promoter in the tissue and serum of colorectal cancer (CRC) patients and to evaluate its clinical relevance. Methods Genomic DNA was extracted from the tissues (cancer tissue and corresponding adjacent normal tissue) and sera of 71 CRC patients; serum genomic DNA was also obtained from 20 patients with benign gastrointestinal diseases and 20 healthy donors. Promoter methylation status of DLEC1 gene was detected by methylation-specific polymerase chain reaction (MSP). Results The incidence of aberrant methylation of DLEC1 promoter was 45.1% (32/71) in CRC tissues, which was significantly higher than that in the adjacent normal tissues (7.1%,4/56) (P<0.001). The hypermethylation status of DLEC1 was not correlated with the clinicopathological features and CEA/CA19-9 levels of CRC patients. Moreover, DLEC1 promoter methylation was also found in 28 of 71 (39.4%) CRC serum samples and only 1 (2.5%) of the other 40 cancer-free serum samples (P<0.001); the methylation was in accordance with that in the tumor tissues. Conclusion Hypermethylation of DLEC1 promoter is frequently seen in CRC patients, suggesting it might be a promising biomarker for the early diagnosis of CRC.