Bell has returned to Elland Road little over a year after he left Leeds’ commercial department to become chief operating officer at fellow Championship side Sheffield Wednesday.
He ran commercial operations at United for almost five years but quit for HIllsborough six months after Massimo Cellino’s takeover of Leeds in April 2014.
United have been without an executive director since Pearson unexpectedly quit the post in September of this year.
Pearson, the former Hull City chairman, linked up with Cellino in May and oversaw a productive summer of recruitment but stepped down suddenly a month and a half into this season, citing personal reasons for his resignation.
As chief executive, Pearson was seen a key conduit between Cellino and United’s then first-team boss Uwe Rosler.
Rosler was sacked a month after his departure and replaced by Steve Evans.
Cellino told United’s official website: “Paul already has the knowledge of Leeds United and the experience needed to help continue to take us forward off the field.
“Sheffield Wednesday were very disappointed to lose Paul and it’s not difficult to see why.”
Bell said: “I’m immensely honoured to return to Leeds United and I’m relishing the opportunity to work alongside Massimo Cellino in leading the business side of the club and the senior management team.
“I also look forward to supporting Steve Evans, his first-team staff, players and everybody at Thorp Arch during what I feel is a particularly exciting time for the club.
“During my previous time here, I helped the club reach its strongest commercial footing for nine years – an achievement which I’m incredibly proud of and something I’m aiming to build on this time around.”