Conventional tumor models have historically failed to fully recapitulate the intricate pathophysiological complexity and dynamic microenvironment of human malignancies, significantly limiting their translational potential. The recent convergence of microfluidic technology and 3D bioprinting has ushered in a paradigm shift in oncology research, enabling more physiologically relevant models. This review provides a comprehensive analysis of the limitations inherent in traditional tumor modeling platforms and elaborates on the fundamental principles underlying microfluidics and additive manufacturing. We systematically explore the integrated applications of 3D-bioprinted microfluidic systems across three core domains: engineering pathomimetic tumor models, advancing therapeutic screening platforms, and developing high-sensitivity diagnostic tools. This interdisciplinary synergy allows for unprecedented spatiotemporal control over the tumor microenvironment, precise biochemical gradient formation, and seamless integration of functional biosensors. We further discuss persistent challenges—such as material biocompatibility, fabrication scalability, and the need for standardized validation—and propose future directions, including the development of multi-organ-on-chip systems, stimuli-responsive biomaterials, and AI-enhanced analytical frameworks. The continued integration of 3D bioprinting and microfluidics holds transformative potential for accelerating precision oncology and improving clinical outcomes.