Leeds started well enough and almost took the lead in the sixth minute but Eirik Bakke's low shot hit the foot of the post with keeper Joe Murphy well beaten.
It looked encouraging for a while as they pushed forward with determination and Jermaine Beckford was twice flagged for offside in his eagerness to impress.
The Whites did take the lead five minutes before the break when Robbie Blake struck a right-foot shot past sub keeper Josh Lillis.
The hosts, who were lively all night, equalised straight away through Matthew Sparrow, who hit home from close range following Dave Mulligan's low cross from a corner that Neil Sullivan probably should have done better from.
They scored their second goal after 51 minutes when substitute Billy Sharp rose above a sleepy Leeds defence to head past Sullivan.
Leeds had French striker Garra Dembele as a trialist in the 2nd half when he replaced Beckford up front. The French U20 international had a trial at Newcastle but did not earn a deal at St James' Park.
Bakke then had a reasonable chance in the 75th minute from near the penalty spot, but shot wide.
The Whites: Sullivan, Kelly, Parker, Livermore, Gregan, P. Butler, Richardson, Bakke, Beckford (Garra Dembele h/t), Blake, Carole.
Subs Unused: Griffiths, Bennett, Rose, Morris, Bayley, Hird, Howson.
Scunthorpe Utd: Murphy (Lillis 39min), Mulligan (Asamoah 77min), Ridley, Crosby (Foster h/t), Hinds, Byrne, Sparrow, Torpey, Baraclough (Twibey 85min), A. Butler (Williams 62min), Keogh (Sharp h/t).
Subs Unused: Goodwin.