"Today, I am announcing my resignation as a Member of the United States House of Representatives effective March 31," Schock, 33, wrote in a statement.
Schock wrote that “constant questions” over the past six weeks “have proven a great distraction that has made it too difficult for me to serve the people of the 18th District with the high standards that they deserve and which I have set for myself.”
“I have always sought to do what's best for my constituents and I thank them for the opportunity to serve," he added.
Schock did not notify House Republican leaders prior to his decision to resign, catching the GOP leadership off-guard, according to a senior GOP leadership aide.
“With this decision, Rep. Schock has put the best interests of his constituents and the House first," House Speaker John Boehner wrote in a brief statement. "I appreciate Aaron’s years of service, and I wish him well in the future."
In Illinois, Republican Governor Bruce Rauner said it was "a sad day for the people of Illinois and the 18th District" in a statement after Schock's announcement.
Schock came under fire last month for his spending on office décor, which bore a striking resemblance to the one featured in the popular PBS British drama series, "Downton Abbey," as well as eyebrow-raising travel spending.
He has hired a team of lawyers from the Washington, D.C., firm Jones Day, as well as communications operatives Ron Bonjean and Brian Walsh -- both veteran congressional aides -- to help him respond to his recent troubles.
The Office of Congressional Ethics had reportedly launched an investigation into Schock's spending habits, although that probe will end once Schock's resignation is official.
Schock was already under investigation by the House Ethics Committee for allegedly soliciting contributions for an independent expenditure-only political committee in excess of $5,000 per donor, in violation of federal law, House rules, and standards of conduct. That investigation will also end on March 31st once the resignation takes effect, although Schock could still potentially face a criminal inquiry.
A Schock spokesperson confirms that Schock has repaid all money he’s received during his congressional career from expensing mileage.
“In an effort to remove any questions and out of an abundance of caution, Congressman Schock has reimbursed all monies received for official mileage since his election to Congress,” a Schock aide wrote in an email.