It might have been different if Hull had not struck the woodwork with the game scoreless but the promotion-chasers created little else up front.
Oldham were first to threaten when Will Haining, converted from defence to midfield, headed narrowly over the bar.
Haining was forced off with a hamstring injury but not before Neil Kilkenny had blasted a 30-yard drive just beyond the far post.
Leon Cort headed off target for Hull but they were back under pressure before half time, a last-ditch clearance denying Oldham from a corner.
The home side were on top after the break as Luke Beckett and Mark Hughes both went close with headers.
Hull's unfortunate brush with the woodwork came when Cort went forward for a corner and saw his powerful header thud against the post before rolling along the line with no-one able to find the finishing touch.
Oldham's breakthrough came on 71 minutes when Kilkenny bent over a free-kick from the left and Killen sent a glancing ten-yard header inside the far post.
They could have been pegged back within five minutes but Tigers substitute Jason Price dragged his shot wide when in acres of space deep inside the box.
Fellow substitute Aaron Wilbraham, who had a long spell with Oldham earlier in the season, was sent on in a last-ditch bid to snatch a point by Tigers boss Peter Taylor.
Wilbraham was inches wide with his first touch but Oldham clung on in the dramatic closing stages.