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Tsunami wave observations far from the coast remain challenging due tothe logistics and cost of deploying and operating offshoreinstrumentation on a long-term basis with sufficient spatial coverageand density. Distributed Acoustic Sensing (DAS) on submarine fiber opticcables now enables real-time seafloor strain observations over distancesexceeding 100 km at a relatively low cost. Here, we evaluate thepotential contribution of DAS to tsunami warning by assessingtheoretically the sensitivity required by a DAS instrument to recordtsunami waves. Our analysis includes signals due to two effects induced by thehydrostatic pressure perturbations arising from tsunami waves: thePoisson’s effect of the submarine cable and the compliance effect of theseafloor. It also includes the effect of seafloor shear stresses andtemperature transients induced by the horizontal fluid flow associatedwith tsunami waves. The analysis is supported by fully coupled 3-Dphysics-based simulations of earthquake rupture, seismo-acoustic wavesand tsunami wave propagation. The strains from seismo-acoustic waves andstatic deformation near the earthquake source are orders of magnitudelarger than the tsunami strain signal. We illustrate a data processingprocedure to discern the tsunami signal. With enhanced low-frequencysensitivity on DAS interrogators (strain sensitivity ≈2×10 at mHz frequencies), we find that, on seafloorcables located above or near the earthquake source area, tsunamis areexpected to be observable with a sufficient signal-to-noise ratio withina few minutes of the earthquake onset. These encouraging results pavethe way towards faster tsunami warning enabled by seafloor DAS.