A search for the rare two-body decays Λb → D0Λ and Ξb → D0Λ is performed with proton-proton collision data, corresponding to an integrated luminosity of 6 fb-1, collected by the LHCb experiment at a center-of-mass energy of 13 TeV. The decay Λb → D0Λ is seen with a statistical significance of 5.5 standard deviations, and constitutes the discovery for this decay. The branching fraction, measured using the Λb → D0pπ- decay for normalization, is (9.9 ± 2.3 ± 1.6 ± 1.1) × 10-6, where the uncertainties are statistical, systematic, and external, respectively. An excess of Ξb → D0Λ candidates w.r.t. the background is observed with a statistical significance of 1.8 standard deviations and is used to estimate the upper limits.