A measurement of the Λ0b lifetime and mass in the decay channel Λ0b→J/ψ(μ+μ−)Λ0(pπ−) is presented. The analysis uses a signal sample of about 2200 Λ0b and Λ0b decays that are reconstructed in 4.9  fb−1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Λ0b lifetime and mass. They are measured to be τΛb=1.449±0.036(stat)±0.017(syst)  ps and mΛb=5619.7±0.7(stat)±1.1(syst)  MeV.