The progression of cancer is strongly influenced by the crosstalk between cancer cells and immune cells. Immune cells can have both pro- and anti-tumor functions depending on the signals present in the environment. A significant proportion of the immune compartment of most solid tumors consists of tumor-associated macrophages. Although their abundance has been associated with poor prognosis in many solid tumor types, the molecular mechanisms by which cancer cells influence macrophage phenotype and function are largely unknown. In this chapter, we provide a detailed description of in vitro assays to study the impact of cancer cells on macrophages. We provide protocols to obtain macrophages from murine bone marrow and human peripheral blood, and to expose these macrophages to cancer cell-derived secreted molecules using conditioned medium from cancer cells. We describe several assays to assess cancer cell-induced polarization of macrophages. This experimental set-up can be utilized to gain molecular insights into how cancer cells influence macrophages.