WATCH: Grimbsy Town 1 Sheffield United 3 - Billy Sharp on target twice
Dominic Calvert-Lewin was also on the scoresheet as Chris Wilder's team, who continue their pre-season preparations against Derby County on Wednesday, recorded a deserved win at Blundell Park.
Barnsley's Kayden Jackson featured for Paul Hurst's side after completing a loan move from Oakwell.
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Hide AdWith Adams starting on the bench after being the subject of a £1.2m bid from Birmingham City earlier in the week, Calvert-Lewin seized his opportunity by edging the visitors into a 23rd minute lead. Sharp's through ball sent the youngster through and, following a deft chip and touch, he turned the ball home from close range.
Calvert-Lewin, who was replaced by Marc McNulty at half-time, turned provider two minutes later when his cross set in motion the chain of events which ended with Sharp doubling United's advantage.
James Wilson had an attempt hacked clear before Luke Summerfield pounced for Grimsby.
But Sharp responded by sliding the ball home on the hour to put Wilder's side, missing Louis Reed through injury, back in control.
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Hide AdGrimsby Town: McKeown, Davies, Andrew, McAllister (Bogle 46), Pearson (Boyce 70) , Gowling, Chambers (M Wright 85), Jackson, Vose (Disley 70), Berrett, Summerfield. Not used: Venney, Clifton, Jones.
Sheffield United: Long, Brayford (Freeman 87), Wilson, O'Connell, Hussey (K Wallace 87), Basham (Whiteman 83), Fleck (Brooks 78), Duffy (Scougall 67), Done (Coutts 67), Calvert-Lewin (McNulty 46), Sharp (Adams 61). Not used: Ramsdale, Semple, J Wright.
Referee: David Webb.
Attendance: 3760 (1808 away).