David Connolly gave Leicester a first half lead, squeezing in a left-footed shot from the tightest of angles for his 11th goal of the season.
But 10 minutes after the break Ardley got his first for the club, curling in a free kick from just outside the box.
Dion Dublin hit the bar, before Nikos Dabizas was sent off for a second bookable offence. James Collins narowly missed a Cardiff winner near the end.
Cardiff manager Lennie Lawrence:
"We started okay and then got battered for half an hour but thanks to our goalkeeper [Neil Alexander] we were kept in the game.
"We had stood off them and they played around us, causing us problems, but I felt in the second half we were the better team and deserved our goal.
"We have stopped the rot after a couple of defeats, but we are not out of it by any means."
Leicester: Walker, Kenton (Stearman 82), Dabizas, McCarthy, Maybury, Hughes (Gillespie 86), Williams, Nalis, Tiatto, Connolly (de Vries 90), Dublin. Subs Not Used: Moore, Hirschfeld.
Sent Off: Dabizas (81).
Booked: Dabizas, Maybury, McCarthy, Stearman.
Goals: Connolly 33.
Cardiff: Alexander, Vidmar, Collins, Gabbidon, Barker, Ardley (Ledley 90), Boland, Langley, McAnuff, Thorne, Jerome (Lee 64). Subs Not Used: Margetson, Parry, Williams.
Goals: Ardley 58.
Ref: P Taylor (Hertfordshire).