Devaney began his career in law enforcement in 1968 as a Massachusetts police officer. After graduating from Franklin and Marshall College in 1970 with a degree in Government, Devaney became a Special Agent with the United States Secret Service.
Devaney served as the Special Agent in Charge of the Fraud Division until his retirement from the Secret Service in 1991, by which time he had gained international recognition as an expert on white-collar crime, and was regularly sought by major media organizations. During his tenure with the Secret Service, Devaney received five U.S. Department of Treasury Special Achievement Awards, as well as numerous honors and awards from several professional organizations.
Upon leaving the Secret Service, Devaney became the Director of Criminal Enforcement for the United States Environmental Protection Agency. In this position, Devaney oversaw all of EPA's criminal investigators and assumed management responsibility for EPA's Forensics Service Center [NEIC]and the National Enforcement Training Institute. Devaney's years of managerial excellence were recognized in 1998 with a Presidential Rank Award.
During his tenure at the Department of the Interior, Devaney helped to investigate disgraced ex-lobbyist Jack Abramoff, oversaw the criminal conviction of the Deputy Secretary J. Steven Griles which ultimately led to the resignation of the Department Secretary Gale Norton. Devaney also investigated Julie A. MacDonald, Deputy Assistant Secretary at the Interior Department who had been appointed by Norton in 2002. MacDonald also resigned after Devaney found that she had violated federal rules by giving government documents to industry lobbyists. Because of Devaney's findings, the US Fish and Wildlife Service ordered the review of eight endangered species decisions in which MacDonald was involved. Devaney called MacDonald's management "abrupt and abrasive, if not abusive," and U.S. Senator Ron Wyden, who commissioned the report, attributed the "untold waste of hundreds of thousands of taxpayers' dollars" to MacDonald's actions.
In 2008 Devaney investigated allegations of wrongdoing by a dozen current and former employees of the United States Minerals Management Service, and found that "a culture of ethical failure" pervaded the agency. Devaney's investigation found that eight officials accepted gifts from energy companies, whose value exceeded limits set by ethics rules. The investigation also concluded that several of the officials "frequently consumed alcohol at industry functions, had used cocaine and marijuana, and had sexual relationships with oil and gas company representatives." According to the New York Times, "The reports portray a dysfunctional organization that has been riddled with conflicts of interest, unprofessional behavior and a free-for-all atmosphere for much of the Bush administration’s watch."
In February 2009, U.S. President Barack Obama announced his choice of Devaney to be the Chairman of the Recovery and Accountability Board to oversee the $787 billion American Recovery and Reinvestment Act of 2009. In that role, he was heralded by the national media for ushering in a new era of accountability and transparency in American government.
Devaney retired from federal service in December 2011. He currently serves on several corporate and non-profit Boards.