In most cases, metastatic colorectal cancer is not curable, thus new approaches are necessary to identify novel targets for colorectal cancer therapy. Actin-binding-proteins (ABPs) directly regulate motility of metastasising tumor cells, and for cortactin an association with colon cancer metastasis has been already shown. However, as its depletion only incompletely inhibits metastasis, additional, more suitable cellular targets have to be identified. Here we analyzed expression of the ABPs, DIAPH1, VASP, N-WASP, and fascin in comparison with cortactin and found that, besides cortactin, DIAPH1 was expressed with the highest frequency (63%) in colorectal cancer. As well as cortactin, DIAPH1 was not detectable in normal colon tissue and expression of both proteins was positively correlated with metastasis of colorectal cancer. To analyse the mechanistic role of DIAPH1 for metastasis of colon carcinoma cells in comparison with cortactin, expression of the proteins was stably down-regulated in the human colon carcinoma cell lines HT-29, HROC-24 and HCT-116. Analysis of metastasis of colon carcinoma cells in SCID mice revealed that depletion of DIAPH1 reduced metastasis 60-fold and depletion of cortactin 16-fold as compared with control cells. Most likely the stronger effect of DIAPH1 depletion on colon cancer metastasis is due to the fact that in vitro knock down of DIAPH1 impaired all steps of metastasis; adhesion, invasion and migration while down-regulation of cortactin only reduced adhesion and invasion. This very strong reducing effect of DIAPH1 depletion on colon carcinoma cell metastasis makes the protein a promising therapeutic target for individualized colorectal cancer therapy. What's new? While cortactin - an actin-binding protein (ABP) and prognostic marker - has been associated with colon cancer metastasis, its depletion only incompletely inhibits metastasis of colon carcinoma cells. By comparing expression of various ABPs in colorectal cancer samples, here the authors found that, in addition to cortactin, expression of DIAPH1 positively correlated with metastasis. Down-regulation of DIAPH1 reduced metastasis of colon cancer cells in SCID mice 60-fold, and significantly inhibited adhesion, invasion, and migration in vitro. Knockdown of cortactin reduced metastasis 16-fold and only inhibited adhesion and invasion. Thus, DIAPH1 is a promising new target for inhibition of colon cancer cell metastasis.