Midfielder Gary Dicker joins from Carlisle United on an 18-month deal and full-back Lee Hodson arrives on loan from MK Dons.
Dicker, 29, has made 27 appearances this season and was due to be out of contract with the English League Two side in the summer.
Hodson, 24, is a Northern Ireland international, winning the first of 14 caps in 2010.
He has only featured in three league matches this season, having helped MK Dons win promotion to the Championship last term.
Dublin-born Dicker started Carlisle's 3-0 FA Cup loss to Everton on Sunday, the day after Gary Locke resigned at Rugby Park.
Meanwhile, Lee McCulloch will take charge of Killie's Scottish Cup tie against Rangers on Saturday.
The former Ibrox captain, 37, was recruited by Locke as a player-coach in the summer.
Killie are still in talks with the former Motherwell and Nottingham Forest boss Billy Davies over their managerial vacancy.
But those discussions are unlikely to be concluded before the weekend.
Managerless Kilmarnock have added two new signings on transfer deadline day.