Prostate cancer is the most common cancer in men. In recent years, several new targeted therapeutic agents for the treatment of metastatic castration resistant prostate cancer (mCRPC) have been developed. These include androgen receptor targeting agents, new taxanes, radium-223, and immunotherapies. In this short review, we provide a summary of clinical and preclinical biomarkers for each of these new treatment strategies, also including new markers currently presented in conference papers only. Moreover, we address the role of these biomarkers in clinical routine with the aim to select best-personalized treatment strategies for patients. Finally, we provide a decision tree for selecting the proper therapy for patients with mCRPC according to the discussed biomarkers.