The potential toxicity of nanocarrier excipients and complicated preparation technologies have impeded the clinical application of nanomedicine. Recently, pure drug-assembled nanosystems (PDANS) have been widely investigated, due to the unique self-assembly characteristics of pure drug molecules. PDANS provides a facile nanoplatform for developing carrier-free nanomedicine. Herein, the recent trends in PDANS for cancer therapy are outlined. First, the emerging strategies to develop single pure drug-based nanoassemblies are discussed. Second, co-assembly of two or more pure drugs for efficient combination therapy is overviewed. Then, the functional self-assembly of non-cytotoxic agents in tumor sites is presented. Finally, the rational design and self-assembly mechanisms of these unique nanoplatforms are highlighted.