(Ti,Zr)C synthesized and aged in the immiscibility temperature range was investigated to improve understanding of the mechanism of phase separation, particularly the nucleation and early growth stages. The phase separation was observed to occur through discontinuous precipitation at grain boundaries. The nuclei were found enriched in titanium and associated with dislocations intersecting grain boundaries. During growth, zirconium enriched regions form subsequently and the semi-coherent interfaces of the Ti- and Zr-rich phases contain misfit dislocations. These observations suggest that dislocations play an important role for the nucleation and growth during discontinuous precipitation in the (Ti,Zr)C high misfit miscibility gap system.