Eppiah converted a cross from substitute Liandro Martis to take the Foxes, who have already qualified for the last 16, five points clear at the top of Group F.
Substitute Leon Maloney had given Pompey a 70th-minute lead from Jez Bedford's centre.
The dropped points mean Portsmouth finish on five points after completing their fixtures, one point behind second-placed Everton.
The top two from each of the eight groups progress to the knockout stages.
Leicester: 19 Feb v Arsenal (H) PL2