The fundraiser is scheduled for September in East Brunswick, N.J., for the Republican governor's 52nd birthday, according to the report.
Christie is a potential candidate for president in 2016. And Romney, the 2012 GOP nominee, has called the New Jersey governor a strong candidate, along with a number of other Republicans.
Romney has defended Christie in the past and said the scandal involving the closure of toll lanes on the George Washington Bridge would not hurt his potential bid.
Christie was one of the first governors to endorse Romney during the 2012 campaign. But Republicans criticized Christie after he toured the Jersey Shore with President Obama following a devastating hurricane days before the election, an image some said boosted the president and hurt Romney.
Last year, Romney had to apologize to Christie after details of his campaign's vetting process of Christie for his vice presidential running mate leaked. The campaign reportedly had a number of reservations about Christie and eventually settled on Rep. Paul Ryan (R-Wis.) for the slot.