Phased array technology operates through the high-precision electronic regulation of excitation phase and amplitude across multi-channel array elements to achieve inertia-free beam steering, spatial focusing, and dynamic scanning. Originally developed in radar and wireless telecommunications, the technology has progressively expanded into medical diagnostics and therapeutics, emerging as a foundational pillar of precision medicine. To prevent conceptual generalization and establish rigorous physical boundaries, this review explicitly delineates three technical tiers: strictly defined phased arrays governed by coherent wave interference; multi-coil electromagnetic systems guided by spatial field modulation concepts; and generalized array-based architectures employing multi-channel spatial encoding or high-speed temporal scanning. In diagnostic imaging, strictly defined acoustic and microwave phased arrays have enhanced spatial and temporal resolution, accelerating the advancement of flexible wearable ultrasound patches, microelectromechanical piezoelectric arrays, and non-contact vital sign radar sensors. Concurrently, generalized array frameworks have provided critical architectural support for mainstream clinical modalities: multi-channel magnetic resonance imaging (MRI) receive coil arrays exploit localized spatial sensitivity profiles for parallel acquisition acceleration and signal-to-noise ratio enhancement, rather than active beam synthesis; meanwhile, distributed cold-cathode X-ray source arrays in static computed tomography (CT) replace mechanical gantry rotation with microsecond-to-millisecond temporal electronic switching, substantially mitigating motion artifacts while fundamentally differing from wave-interference phased arrays. In precision therapeutics, phased array systems leverage precise energy deposition capabilities to achieve non-invasive or minimally invasive intervention in deep-seated lesions. Focused ultrasound (FUS) and microwave hyperthermia systems combine physical matching media, medical-image-based tissue modeling, and multi-channel adaptive phase compensation to overcome severe beam refraction and wavefront aberrations across heterogeneous tissues such as skull and breast. Furthermore, multi-coil electromagnetic systems apply phased-array spatial field shaping principles to quasi-static or low-to-medium frequency fields; by optimizing the pulse repetition frequency of rapid transient magnetic fields in transcranial magnetic stimulation (TMS) and managing high-frequency currents in magnetic hyperthermia (MHT), these arrays achieve localized field enhancement and preserve scalp safety via spatial vector superposition. Translating these advanced array systems from laboratory validation into clinical practice encounters significant physical and engineering hurdles. At the physical and computational level, high-density array integration intensifies inter-element mutual coupling, while phase aberration corrections across complex tissues substantially increase the computational burden, data throughput, and optimization dimensionality. At the engineering and regulatory level, massive high-power transmit modules introduce critical thermal management bottlenecks, while industrial manufacturing repeatability across thousands of channels, long-term biocompatibility of flexible materials, and the interpretability of artificial intelligence algorithms remain essential hurdles for medical device approval. Looking forward, the biomedical phased array domain is evolving toward portable wearable integration, intelligent adaptive beamforming, and multimodal closed-loop theranostics. Deep learning algorithms demonstrate strong potential to mitigate optimization overhead and execute real-time aberration corrections. Concurrently, edge computing helps reconcile channel density with thermal dissipation constraints, and the synergistic integration of real-time imaging feedback with adaptive energy delivery will redefine personalized non-invasive precision intervention.