The sum includes $3.2 million in direct investigation expenses covering things like pay, supplies and rent; $1.7 million was for salary and benefits.
The federal government spent almost $7 million investigating Russian meddling in the presidential election between May and September, the Justice Department announced Tuesday.
Mueller honed in on Trump's former and current dealings with the German bank as the U.S. investigation into potential Russian meddling allegations during the U.S. elections.
Mueller was appointed special counsel in May, after President Donald Trump fired Federal Bureau of Investigation director James Comey.
The details of the expenditures related to Mueller's investigation were laid out in a report released publicly by the special counsel's office. Mueller reports to Deputy Attorney General Rod Rosenstein, who appointed him, although the rule gives a special counsel broad discretion to run the investigation without regularly consulting with the department or requesting its approval.
Funds were spent on personnel, travel and office space, the Justice Department said. In October, the first indictments in his probe were unsealed in court against Trump's former campaign manager Paul Manafort and an aide, Rick Gates.More news: Liverpool win Group E with Coutinho hat trick
The private practice lawyers who joined Mueller's office each gave up more than a million dollars in annual pay, according to their previously reported financial disclosures.
His team has issued subpoenas for documents and testimony to a handful of figures, including some people close to Manafort, and others involved in the June 2016 Trump Tower meeting between Russians and campaign officials.
Special counsel Robert Mueller's investigation of possible coordination between the Trump campaign and Russian Federation to influence the 2016 election cost the government about $6.7 million in Mueller's first four and a half months in office, according to a report released by the Justice Department on Tuesday.
Although the expenditures that took place between mid-May and September 30 for the special counsel's operations are relatively low compared with what many had anticipated, they could provide additional fodder for Republicans who have been critical of Mueller's work. Two have pleaded guilty.
Though Mueller's investigation is not yet a year old, his team of prosecutors have made significant moves. "I continue to strongly support Bob Mueller's investigation and believe he should receive all the resources he needs to follow the facts and the law where they lead".