The impressive figure, a record for the 2012 presidential campaign, excludes the millions raised by independent groups that support 65-year-old Romney, a former Massachusetts governor.
President Barack Obama and the Democratic Party have not yet released their fundraising results for June.
In May, the Romney campaign out-fundraised its rival, attracting USD 77 million against the Obama team's USD 60 million.
Obama, 50, seeking re-election in November, has been warning his supporters that he is in danger of becoming the first sitting president in history to be outspent by his opponent.
According to Romney's campaign aides, much of the money raised in June came from new donors, Politico reported.
Several states, including the key battlegrounds of Colorado, Michigan and Ohio, exceeded their fundraising goals, the aides were quoted as saying.
Fundraising is crucial to US presidential elections, when candidates undertake extensive tour of the country and launch several advertising blitz, spending hundreds of millions of dollars to woo the voters.