The Philippi peat, NE Greece, constitutes one of the largest fossil fuel deposits in the Balkans and its potential use for power generation cannot be ruled out in the future. In this study, the concentrations of 43 trace elements (Ag, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Ga, Gd, Ge, Hf, Ho, La, Li, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Sm, Sn, Sr, Ta, Tb, Th, U, V, W, Y, Yb, Zn, and Zr) in the 550 °C peat ashes are determined and related to the concentrations in the bulk peat, to evaluate the behavior of each element during combustion. Mineralogical analysis of the chemically oxidized peat samples revealed that clay minerals, feldspars, quartz, gypsum, and calcite are the dominant mineral phases. The behavior of the trace elements during combustion depends significantly on this mineral composition that, in turn, depends on the depositional conditions during peat accumulation.