The current scope and status of the ATLAS B-physics trigger and of off-line performance studies are presented. From the initial running at low-luminosity at LHC, high-statistics B analyses will allow sensitive tests of possible new physics contributions by searching for additional CP violating effects and for anomalous rates of rare B-decay channels. In the physics of the B0s meson system there is sensitivity to mass and width differences and to a weak mixing phase beyond the Standard Model expectation. ATLAS will also be able to access rare B decays using the high-luminosity running. Measurements of beauty production sensitive to higher order QCD terms will also be made, providing new data to investigate present inconsistencies between theory and experiment.