The theoretical modeling of lanthanide and actinide complexes in condensed media (in solution, at interfaces or in the solid state) is challenging for theoretical chemistry, due in part to the intrinsic general challenge of devising a reliable model of the species in such environments and the necessity of ‘spectroscopic’ or ‘chemical’ accuracies. One of the promising quantum chemical approaches to treat large systems is the frozen-density embedding theory, in which various levels of theory (wave-function theory and/or density functional theory) can be combined by partitioning the total density into interacting densities of the composing subsystems. We will present on-going methodological developments and applications of this approach to the study of optical transitions and NMR chemical shifts of actinide systems.