Ian Murray, who became Shadow Scottish Secretary earlier this month after the General Election, is to stand down as a Hearts director at the end of June.
Murray was left as the only Labour MP in Scotland after being returned for the Edinburgh South constituency.
He joined the board last summer as a Foundation of Hearts representative when the club exited administration.
"I have to devote my time to my constituents and my responsibilities in parliament," he told BBC Scotland.
"My spare time has vanished since being appointed to the shadow cabinet but also being the only Labour MP in Scotland.
"I leave with an incredibly heavy heart but I think the Foundation and the football club are in fine fettle for the future."
The fans' group was a key player in the survival of the Edinburgh outfit.
The end of June will also mark one full year since Ann Budge took over the majority shareholding at the club.
An official statement is expected to be made by the Edinburgh club in the next few days.