Mayor Bill de Blasio’s biggest campaign boosters over the past six months include Hollywood celebs promoting his progressive agenda and former top staffers who left him for the private sector.

De Blasio’s re-election campaign reported pocketing $1,073,908 in donations since mid-July and spending $592,606, according to his latest filings submitted Tuesday to the city’s Campaign Finance Board.

Although more than four-fifths of the 3,261 new donations were under $250, de Blasio scored $4,950 — the maximum allowable under campaign finance laws — from dozens of supporters. The big donors include actors Steve Buscemi and Cynthia Nixon, designer Diane von Furstenberg, composer Jonathan Scheffer, de Blasio’s former communications director Karen Hinton, who left City Hall last year, and former senior adviser Peter Ragone, who left in 2015.

The campaign’s key expenses over the six months included shelling out $60,045 in consulting fees to Ross Offinger and another $42,500 to the firm BerlinRosen. As part of a widening probe of City Hall, the feds have been looking at past fundraising activities for de Blasio by Offinger and political consulting work by staffers at BerlinRosen.

With the latest filing, de Blasio has now amassed a campaign war chest of $3.3 million for his re-election bid and has $2.2 million in hand.

However, he was outraised and outspent over the past six months by deep-pocketed developer Paul Massey, a political novice running as a Republican for mayor who raised $2.9 million. This includes nearly $1.63 million in donations — slightly more than half that came from donors living outside the city — and $1.27 million of his own money that he loaned to the campaign.

Massey, who only kicked off his fundraising in August, has already spent a whopping $1.8 million on his campaign — much of it on staff and consultants.

Others who announced candidacies to run for mayor include former NYPD detective Bo Dietl, who raised $282,656 since mid-July; former New York Jet-turned-minister Michel Faulkner, who raised $206,591; and state Sen. Tony Avella, who raised $750 after kicking off his candidacy last month.

Comptroller Scott Stringer, who is considering a mayoral run but has not declared his intentions yet, raised $346,961 over the past six months. His campaign fund has raised more than $2 million and has $1.7 million in hand.