The most commonly occurring sarcoma of the soft tissue is gastrointestinal stromal tumor (GIST). Treatment and prevention of the disease necessitate an understanding of the molecular mechanisms involved. However, the role of BRD4 in the progression of GIST is still unclear. While it is known there are abundant infiltrating tumor-associated macrophages (TAMs) in the tumor microenvironment, the exact role of these cells has yet to be studied. This work showed an upregulation of BRD4 in GIST that was associated with GIST prognosis. Through gain and loss of function studies, it was found that BRD4 promotes GIST growth and angiogenesis in vitro and in vivo. Mechanistically, BRD4 enhances CCL2 expression by activating the NF-κB signaling pathway. Furthermore, this CCL2 upregulation causes recruitment of macrophages into the tumor leading to tumor growth. A likely mechanism for interactions in the GIST microenvironment has been outlined by this work to show the role and potential use of BRD4 as a treatment target in GIST.