ABSTRACT. We formulate a rigorous method for calculating a nonadiabatic (frequencydependent) exchange-correlation (XC) kernel required for correct description of both equilibrium and nonequilibrium properties of strongly correlated systems within Time-Dependent Density Functional Theory (TDDFT). To do so we use the expression for charge susceptibility provided by Dynamical Mean Field Theory (DMFT) for the effective multi-orbital Hubbard Model. We tested our formalism by applying it to the one-band Hubbard model: our nonadiabatic kernel leads to a significant modification of the excitation spectrum, shifting the peak that appears in adiabatic (simplified) solutions and disclosing a new one, in agreement with the DMFT solution. We also used our method to track the nonequilibrium charge-density response of a multi-orbital perovskite Mott insulator, YTiO 3 , to a perturbation by a femtosecond (fs) laser pulse. The results were quite different from those provided by the corresponding adiabatic formalism. These initial investigations indicate that electron-electron correlations and nonadiabatic features can significantly affect the spectrum and nonequilibrium properties of strongly correlated systems. Introduction.--Correct description of the physical, including nonequilibrium, properties of strongly correlated electron systems is one of the most important goals of the condensed matter and material science communities. These systems demonstrate unusual properties with many potential applications both in bulk (high-temperature superconductivity, exotic interplay of magnetism and superconductivity, giant magneto-resistance, etc.) (see, for example Ref.[1]) and in the nanocase (for example, antiferromagnetism in small Fe chains, 2 exotic charge carrier generation in the insulating phase of a VO 2 nanosystem, 3 and anomalous lattice expansion 4,5 and room temperature ferromagnetism 6 in CeO 2 nanostructures). From the perspective of technological applications, nanostructures look even more promising than bulk, since they afford additional channels for tuning a system's properties by varying its size and geometry and by putting it on different substrates. Description of experimentally observed properties as well as prediction of new strongly correlated systems with desired properties requires reliable theoretical and computational tools.