In this study, the influence of topologically close-packed (TCP) phase precipitation on the lattice misfit and coherency stress of the high rhenium and ruthenium containing single crystal Ni-base superalloy LDSX8 was investigated. Even in the standard heat-treated state TCP phases are found in the dendrite cores (DC). With additional annealing at 1100 °C for up to 4 h, further TCP phases precipitate near the DCs. At longer aging times up to 1000 h, the TCP particle shape changes and the initially cuboidal γ′-precipitates become more irregular as coarsening proceeds while the total TCP phase content, as well as the γ′-phase fraction, remain nearly constant after reaching a plateau. The lattice parameter of the γ-phase decreases with increasing exposure time, presumably due to ongoing TCP phase precipitation and the resulting depletion of solid solution strengthening elements within the γ-matrix, and reaches, like the TCP phase fraction, a plateau after long aging times. In contrast, the lattice parameter of the γ′-precipitates does not change significantly during long term annealing, which results in a lattice misfit decrease from about -1 % in the standard heat-treated state to a plateau of about -0.5 % after 100 h. Moreover, the tetragonal distortion of the matrix phase decreases with increasing exposure time, as the coherence stress in the microstructure is relieved and the γ/γ′ interface becomes semi-coherent.