He is the former chairman of the Subcommittee on National Security and Foreign Affairs, where he helped establish the Commission on Wartime Contracting in Iraq and Afghanistan.

He faced tougher challenges after his wife Patrice was convicted of felony tax fraud in 2010, narrowly defeating his Republican opponent in 2012.

His mother, Doris H. (née Gelineau) Tierney, was a Salem native who worked a split shift at the New England Telephone Company, where she remained for 42 years.

When he was young, Tierney campaigned for his uncle, a Peabody ward councilor, and he ascribes his political interest in part to this experience.

As SGA president Tierney responded to racial incidents on campus by organizing a school-wide meeting leading to several days of discussion.

[9] Tierney first ran for Congress in 1994 against one-term Republican incumbent Peter G. Torkildsen, having won a competitive Democratic primary with a plurality of 33.8 percent.

[13][14] In 2010, he faced a stronger challenge from Republican candidate Bill Hudak, after his wife Patrice was convicted of felony tax fraud; he won with 57% of the vote.

[22] In 2010 Washington paper The Hill published a speculation that Tierney, with a $1.3 million war chest, was a likely candidate to run against Kennedy's successor Scott Brown in the 2012 election.

[21][24] Tierney was initially opposed to the Troubled Asset Relief Program proposal of 2008, although he ultimately voted for the bill, saying, "The state of panic in the markets compels Congress to act.

[27] According to the investigation, Tierney has helped direct about $3.5 million toward a 950-space parking garage and commuter rail station in Salem, Mass.

[28] Tierney was a member of the House Committee on Oversight and Government Reform and chairman of the Subcommittee on National Security and Foreign Affairs during the 110th and 111th Congresses.

[35] In June 2000, Tierney's stepson John Chew was arrested when about 25 grams (0.9 oz) of cocaine and $1,000 in cash were found in his Marblehead apartment.

[36][38] In August 2010, Tierney's wife Patrice's brothers Robert and Daniel Eremian were indicted in federal court for operating an illegal internet gambling business.

[35][39] Robert had allegedly, with Daniel's help, operated the business out of St. John's, Antigua and Barbuda, and funneled a portion of the profits into a Bank of America account in Massachusetts.

In October 2010, Patrice was charged in U.S. District Court with four counts of "aiding and abetting the filing of false tax returns" by Robert.

[35] John Tierney issued a statement announcing his wife's intention to plead guilty, stating that Patrice accepted "full responsibility for being 'willfully blind' to what her brother was doing.

[42][43][44] In June 2012, a federal judge ordered Daniel Eremian to forfeit $7.7 million in assets for his role in the illegal offshore sports betting scheme.