Mammalian Sp and Krüppel-like factors (KLF), a family of zinc finger-containing transcription factors, are involved in growth control, proliferation, apoptosis and angiogenesis of a wide variety of tissues and cells. Several KLF have been linked to various types of human cancers, but the relationship between Krüppel-like factor 9 (KLF9) and colorectal cancer has not been explored. The purpose of the present study was to investigate KLF9 expression in human colorectal cancer tissue. KLF9 mRNA was detected on quantitative real-time reverse transcriptase-polymerase chain reaction (Q-PCR). Of the 50 cancerous tissues examined, 86% (43/50) expressed lower levels of KLF9 mRNA than individually matched normal mucosa (P < 0.0001). On western blot, reduced or absent expression of KLF9 protein was observed in 65% (13/20) of the samples (P < 0.01). A total of 81% (35/43) of normal samples had expression of KLF9 protein, whereas its protein was detected in only 9% (4/43) of tumor tissues (P < 0.001) on tissue microarray. These results indicate that KLF9 may be involved in the carcinogenesis of human colorectal cancer.