An iron-based sintered sliding member consists of, by mass %, 0.1 to 10% of Cu, 0.2 to 2.0% of C, 0.03 to 0.9% of Mn, 0.52 to 6.54% of S, and the balance of Fe and inevitable impurities. The iron-based sintered sliding member satisfies the following First Formula in which [S %] represents mass % of S and [Mn %] represents mass % of Mn in the overall composition. The iron-based sintered sliding member exhibits a metallic structure in which pores and sulfide particles are dispersed in the matrix that includes a martensite structure at not less than 50% by area ratio in cross section. The sulfide particles are dispersed at 3 to 30 vol. % with respect to the matrix. [S %]=0.6×[Mn %]+0.5 to 6.0  First Formula