In one aspect the present subject matter is directed to an igniter assembly for a gas turbine engine. The igniter assembly includes an outer housing and an igniter tube that extends radially through the outer housing. The igniter tube includes an ignition tip, a nut coupled to the igniter tube and disposed at least partially within the outer housing and a biasing member that extends between an inner surface of a top portion of the outer housing and the nut. A flexible seal extends radially inwardly from a bottom side of the nut and a retention collar is coupled to the igniter tube proximate to the ignition tip. The retention collar is configured to couple to a mounting ring connected to an outer liner of a combustor for the gas turbine engine.