In 2010, Marino decided to challenge incumbent Democratic U.S. Congressman Chris Carney of Pennsylvania's 10th congressional district. He won the three-candidate Republican primary with 41% of the vote, defeating Dave Madeira (31%) and Snyder County Commissioner Malcolm Derk (28%). On November 2, 2010, Marino defeated Carney 55-45%. In 2012, Marino won re-election to a second term, defeating Democratic nominee Philip Scollo 66%–34%. In 2014, Marino faced off against Independent Nick Troiano and Democrat Scott Brion. Marino garnered 62% of the vote with Troiano received 13% and Brion received 25%. Marino ranked third among Pennsylvania's congressional delegation in Americans for Prosperity's 2012 scorecard (70%) and fifth in the Club for Growth's 2012 scorecard (63%). Marino was a member of the House Baltic Caucus. After a court-ordered redistricting, Marino's district was renumbered as the 12th District ahead of the 2018 elections. It lost its suburban territory closer to Scranton and Wilkes-Barre, in the process losing its last connection to longtime congressman Joseph McDade, who represented the district from 1961 to 1999. To make up for the loss in population, it was pushed slightly westward to take in State College, home to Penn State. The new district was no less Republican than its predecessor, and Marino easily won a fifth term, defeating Democrat Marc Friedenberg with 66 percent of the vote. On January 17, 2019, two weeks after being sworn in for a new term, Marino announced his resignation from the House, to be effective January 23, 2019. Marino described his decision to resign as follows: "Having spent over two decades serving the public, I have chosen to take a position in the private sector where I can use both my legal and business experience to create jobs around the nation." Marino's resignation required a special election to be called by Pennsylvania Governor Tom Wolf via a writ of election within 10 days of Marino's resignation becoming effective on January 23, 2019. Per Pennsylvania law, the special election had to occur no fewer than 60 days following the gubernatorial proclamation being made. On May 21, 2019, Republican Fred Keller won the special election with 68.1% of the vote, defeating his previous 2018 Democratic opponent Marc Freidenberg, and succeeded Marino in Congress. Marino supported the death penalty. He believed that the mentally ill and criminals should not be able to obtain guns. In July 2013, Marino voted against Justin Amash's amendment #413 to H.R. 2397 "To end authority for the blanket collection of records under the Patriot Act and bar the NSA and other agencies from using Section 215 of the Patriot Act to collect records, including telephone call records, that pertain to persons who are not subject to an investigation under Section 215."