Platinum-based chemotherapeutic agents remain among the most effective and widely used drugs in cancer treatment. Since the clinical introduction of cisplatin, platinum complexes such as carboplatin and oxaliplatin have significantly improved therapeutic outcomes in several malignancies, which include testicular, ovarian, colorectal, lung, and bladder cancers. In spite of their remarkable clinical success, the therapeutic application of platinum drugs is frequently limited by severe toxicities, drug resistance, poor selectivity, and interpatient variability in pharmacokinetics. Consequently, accurate monitoring of platinum concentrations in biological systems has become increasingly important for optimizing dosage regimens, minimizing adverse effects, and improving therapeutic efficacy. This review discusses recent advances in the detection and quantification of platinum species in human samples, with emphasis on analytical and imaging techniques employed in clinical and biomedical studies. Conventional approaches such as graphite furnace atomic absorption spectroscopy (GF-AAS), inductively coupled plasma mass spectrometry (ICP-MS), high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and X-ray absorption spectroscopy are critically examined alongside emerging technologies including fluorescence probes, biosensors, electrochemical sensing platforms, and nanotechnology-assisted imaging systems. The review further highlights the role of intracellular platinum tracking, mitochondrial targeting, and single-cell analysis in understanding platinum drug metabolism and mechanisms of resistance. Current challenges and future prospects in platinum monitoring for precision oncology are also discussed.