And on-loan Manchester United striker Welbeck showcased his undoubted class with a delightful chip over visiting goalkeeper Arran Lee-Barrett with six minutes remaining.
The result allowed Preston boss Darren Ferguson to get one over his former Red Devils team-mate Keane as the hosts chalked up their second successive win.
Defeat was harsh on Keane's men, who had lost only one of their previous 15 outings and were neat and tidy in possession but struggled to create genuine goalscoring opportunities.
Preston were not much better, but they upped the tempo after a dreadful first 45 minutes and just about deserved their win.
Ipswich, for whom midfielder Grant Leadbitter was particularly prominent, could have led inside the fourth minute.
Jon Stead showed intelligence to spot Liam Rosenior making tracks inside the right channel and his perfectly-weighted cross found the defender with a clean run on goal.
Rosenior steadied himself 14 yards from goal before blazing a right-footed shot wastefully over the crossbar.
The Tractor Boys' approach play was impressive at times but Preston gradually gained a foothold on proceedings and in the 12th minute a well-flighted cross from Ross Wallace found Chris Brown at the far post.
His header flashed wide and in truth Ipswich goalkeeper Lee-Barrett was all but redundant in the first half.
Ten minutes after the restart, Ipswich were controversially denied an opening goal when striker Tamas Priskin headed a free-kick from the right flank past Preston goalkeeper Andy Lonergan.
The referee's assistant raised his flag, however, and the goal was disallowed.
Yet North End striker Neil Mellor played on and raced upfield before slotting past Lee-Barrett.
Again, the strike was ruled out as referee Jon Moss' whistle had long since blown, but Preston were not to be denied in the 64th minute.
After Collins has replaced Youl Mawene shortly before the hour mark, he quickly made his presence felt with a firm header from Chaplow's fine delivery in the 64th minute.
Keane responded immediately by replacing the ineffective Priskin with Pablo Counago as Ipswich went in search of an equaliser.
However, Ipswich's misery was complete in the 84th minute when Welbeck chipped a superb right-foot shot from 16 yards over Lee-Barrett, who got a hand to the ball but could not prevent it dropping into the net.