The Iron’s top scorer Callum Roberts put them a goal up on 22 minutes and Kian Scales added a second just before the break.
The opening quarter of the game was a closely contested affair but Andy Butler’s Scunthorpe struck the opener with some quick thinking as a free kick was played short to Roberts, who squeezed his finish in off the post for his 18th league goal of the campaign.
Farsley goalkeeper Will Brook made a number of key saves to first deny Will Evans and then Mo Fadera but he was beaten six minutes before the interval as former Celts midfielder Scales chipped the ball over the goalkeeper, and it crept over the line despite the best efforts of Isaac Abankwah.
The visitors almost extended their lead further on 47 minutes when Roberts’ free kick from 25 yards flicked the crossbar before Brook made a phenomenal reflex save to keep out Carlton Ubaezuonu’s effort from close range.
Farsley grew in confidence going forward and in the absence of Harry Sheridan, saw stand-in captain Cole Hyde’s effort from the edge of the box flick the crossbar before Joao Silva’s ambitious long-range effort skimmed the roof of the net.
Scunthorpe had a couple more chances late on with Joe Rowley shooting into the side netting before Mark Beck headed over from close range.
Farsley Celtic: Brook, Bumhira, Abankwah, Polwarth, Mampala, Hyde, Monteiro (Youmbi 41), Priestley-Standing, Kondolo, Silva, Iwobi (Ameho 74).
Subs not used: Edmondson, Krubally.