Cyclin-dependent kinase-like1 (CDKL1) is known as a new member of cyclin-dependent kinases. Whether genetic alterations of CDKL1 gene are involved in the development and/or progression of gastric cancer is still unknown.Here, the expression of CDKL1 protein in paired specimens of gastric cancer tissues and corresponding normal gastric tissue (n = 66) was assessed by immunohistochemistry assay. We then used lentivirus-mediated knock down to specifically inhibit CDKL1 expression in human gastric cancer cell lines. Cell proliferation potential in vitro was measured by MTT and clonogenic assays. Cell apoptosis was assessed by flow cytometry.We show for the first time that high expression of CDKL1 protein was observed in gastric cancer tissues compared with matched adjacent tissues. Loss of CDKL1 function in both SGC7901 and MGC-803 gastric cancer cells significantly decreases cellular proliferation and increases apoptosis (p < 0.01). Furthermore, we show that the reduction of CDKL1 with its siRNA stimulates the activation of Bcl-2-interacting killer (Bik) pro-apoptotic protein and attenuated the expression of proliferating cell nuclear antigen PCNA.In summary, our data suggest that CDKL1 plays an important regulatory role in gastric cancer cell proliferation and survival, and therefore, may represent a new target for therapeutic intervention.