Another gutsy performance from Steve Deakin's new-look Cougars side paid off as they kept their bid to clinch a Northern Ford Premiership play-off spot on track.
The win also sets them up perfectly for Wednesday night's Trans Pennine Cup final against Leigh.
An enthralling battle between two well-matched sides hung in the balance until full back Chris Hogg scored two vital tries midway through the second half to turn the game Keighley's way.
His first came in the 47th minute with the Cougars trailing 10-8.
He was on the spot supporting a great break by Nathan Antonik and James Simeonovich.
Twenty minutes later he was first to a bouncing ball after the hugely influential Rob Roberts had kicked ahead.
Cougars wrapped up their victory in the 70th minute when Antonik and Roberts combined to send Max Tomlinson over wide out.
The Cougars had led 8-6 at the break but there was so little to choose between the sides that picking a winner at that stage was virtually impossible.
Sheffield, who were led superbly by Richard Goddard and Mark Aston, had looked as likely to take victory as the Cougars.
Both sides traded early penalties. Paul Ashton landed the first of his five goals for Keighley just before Goddard landed his only kick for the visitors.
However it was Sheffield who scored the first try when Aston sent Chris Judge crashing through some weak Cougar defence to touch down in the 25th minute.
Goddard missed a relatively simple conversion allowing Keighley to take a narrow half-time lead.
Ashton sent Carlos Sanchez crashing through the Eagles' defence with a neat inside pass just before half-time then landed the conversion to give Keighley that advantage.
Eagles regained the ascendancy just after the break when Gareth Hewitt strolled over with ease to make it 10-8.
Then Hogg stepped up and his two tries sent Keighley on their way to victory and it's difficult to remember that only three weeks ago he was playing Conference rugby at Keighley Albion.
Rob Roberts had a major role in this victory and could yet prove to be a crucial signing as the season draws to a close.
Keighley Cougars: Hogg; Hobson, Hooson, Smith, Tomlinson; Ashton, Antonik; Stephenson, Ramshaw, Hannah, Best, Simeonovich, Sanchez. Subs (all used): Morphet, Shaw, Roberts, Kirk.
Sheffield Eagles: Poynter; Wells, Kite, Hewitt, Thompson; G Brown, Aston; Bruce, Dobson, Brent, Judge, Chapman, Goddard. Subs (all used): Rhodes, Hill, Howieson, I Brown.
Referee: Steve Ganson (St Helens)
Attendance: 1,471
Man-of-the-match: Chris Hogg
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