We report on a search for Λ0b→pπ− and Λ0b→pK− (and charge conjugate) decays in pp collisions at s√=1.96  TeV using 193  pb−1 of data collected by the CDF II experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two-body charmless decays of b-flavored hadrons, including Λ0b baryons. As no Λ0b signal was observed, we set the upper limits on the branching fraction B(Λ0b→ph−), where h is K or π, of 2.3×10−5 at 90% C.L. and 2.9×10−5 at 95% C.L.