Membrane fusion is fundamental to intracellular transport and signal transduction, with its dysregulation implicated in various diseases. Deciphering its transient, microscale dynamics requires advanced sensing technologies. This review systematically evaluates optical and electrochemical sensing platforms for in vitro studies of membrane fusion. Optical sensing platforms provide greater intuitive readout of membrane fusion events, whereas electrochemical sensing platforms enable label-free, single-event resolution. We revisit classical fluorescence resonance energy transfer (FRET) strategies for lipid and content mixing, tracing their evolution from ensemble measurements to real-time, multiparameter, single-vesicle analysis. We further examine electrochemical platforms based on nanodisc-black lipid membranes (ND-BLMs) and solid-supported lipid bilayers (SLBs), highlighting their unique capabilities in characterizing fusion pore kinetics and virus–host membrane fusion. ND-BLM-based systems are irreplaceable for probing fusion pore kinetics, owing to their sub-millisecond temporal resolution and being essentially free from ion saturation and depletion effects. Meanwhile, SLB-based electrochemical sensing platforms excel at high-throughput detection of viral membrane fusion events by virtue of their excellent compatibility and facile integration. These sensors provide powerful tools for elucidating the molecular mechanisms underlying SNARE-mediated membrane fusion and viral fusion processes. Finally, this review outlines future directions centered on the integration of multimodal sensing and the construction of physiomimetic membranes, emphasizing the critical role of cross-scale, multiparameter sensing in bridging molecular mechanisms with biological functions and advancing the diagnosis and treatment of membrane fusion-related diseases.