[1] After being nominated on May 18, 2011 by United States President Barack Obama,[2] Heffern was confirmed by the U.S. Senate on September 26, 2011[3] and sworn in as ambassador on October 6, 2011.

From 1994 to 1996, he served as a Pearson Fellow on the Asia Subcommittee for the House International Relations Committee, for Congressman Doug Bereuter (R-Nebraska).

Initially, U. S. Senator Robert Menendez (D-N.J.) held up Heffern's nomination as a protest against President Barack Obama's "refusal to characterize the Turkish killing of Armenians during World War I as a 'genocide.'"

In the fall of 2011, Heffern expressed his view that Armenia's elections in 2012 and 2013 would be "regarded as democratic," and described his meetings with Armenian president Serge Sargsyan and Foreign Minister Eduard Nalbandian as "'very good'.

Heffern followed his predecessor by posting video blogs on topics related to Armenia and his service in that country to YouTube, under the "usembassyarmenia" tag.