The Rams, without the dropped Lee Camp, started well with Dion Dublin blocking Peter Whittingham's driven shot.
The Foxes upped the tempo, Danny Tiatto forcing a fine save from Kevin Poole, but had to wait until 86 minutes for a goal, Iain Hume stabbing the ball home.
The crowd reacted with a torrent of abuse for under-fire boss Phil Brown before Hamdaoui rifled in the leveller.
Leicester manager Craig Levein:
"In normal circumstances a point away from home would be seen as a good point.
"But after taking the lead with a few minutes to go we're disappointed not to have won.
"Yet again we've played well but not got what we deserved and that's beginning to sound monotonous."
Derby: Poole, Kenna, Davies (Bolder 62), Michael Johnson, Whittingham, Bisgaard, Seth Johnson, Idiakez, Smith, John (Holdsworth 73), Peschisolido (El Hamdaoui 62).
Subs Not Used: Grant, Johnnie Jackson.
Goals: El Hamdaoui 89.
Leicester: Henderson, Stearman (Gerrbrand 45), Dublin, Johansson, Kisnorbo, Hughes (Smith 50), Gudjonsson, Williams, Tiatto, Hammond (de Vries 65), Hume.
Subs Not Used: Sylla, Logan.
Booked: Tiatto, de Vries, Gudjonsson.
Goals: Hume 85.
Ref: D Gallagher (Oxfordshire).