Focal adhesion kinase (FAK) is a non-receptor cytoplasmic tyrosine kinase that transmits signals important in modulating several cell functions, including proliferation, migration, and survival. Several different types of malignant tumors have been reported to express elevated levels of FAK protein in vivo, potentially pointing to a role for FAK in either the progression of tumor cells to malignancy or the pathogenesis of cancer. Considerable knowledge has been gained regarding FAK signaling in non-neoplastic cells, such as fibroblasts, while much less is known regarding FAK signaling in malignant cells. Several studies to date suggest that the regulation of FAK activity and signaling may be different in malignant cells. In this review, we summarize what is known regarding the function and signaling of FAK in cancer cells, and highlight areas that need further study. Evidence is emerging that aberrant FAK expression, activity, and signaling can potentially promote the progression of several types of tumors in vivo through its effects on cell function.