Water parcels in tidal estuaries experience substantial changes in salinity during their tidal excursions, yet the resulting Lagrangian salinity structure and its implications for salt transport remain poorly understood. Here, we employ an idealized estuary to systematically investigate estuarine salinity distribution, exchange flow, and salt transport from a Lagrangian perspective and compare the results with conventional Eulerian and Total Exchange Flow (TEF) frameworks. By tracking water parcels over tidal cycles, the Lagrangian framework characterizes the salinity environments ultimately experienced by transported water masses, thereby providing a transport-oriented description of estuarine exchange. The discrepancy between Lagrangian and Eulerian salt transport is primarily attributed to the transport of Eulerian mean salinity by the approximate Stokes’ drift velocity, with its relative contribution varying along the estuary. Isohaline-coordinate diagnostics further demonstrate that the Lagrangian exchange flow is more consistent with the estuarine volume conservation constraint than conventional Eulerian and TEF estimates. Compared with Eulerian and TEF frameworks, the Lagrangian framework yields fresher inflow and saltier outflow, substantially reducing the salinity contrast between the two exchange branches. Consequently, the conventional interpretation of dominant landward salt transport is weakened, and the saltwater component can contribute to net seaward salt export under certain conditions. These findings highlight the importance of incorporating the salinity environment ultimately experienced by transported water masses into estuarine salt transport analyses and provide new insights into material redistribution in tidal estuaries.