Feeney resigned as a member of Parliament on 1 February 2018 as he was unable to produce any documentary evidence disproving he was a dual citizen, which is a breach of section 44 of the Constitution of Australia.

[2] In 2010, Feeney was one of the key MPs (along with Bill Shorten, Mark Arbib, and Don Farrell) who convinced their colleagues to support Julia Gillard in calling for a leadership spill against sitting Prime Minister Kevin Rudd.

[10] As Parliamentary Secretary, Feeney commissioned the report into Unresolved Recognition for Past Acts of Naval and Military Gallantry and Valour, and was responsible for the Australian Government's Defence Honours and Awards Appeals Tribunal.

He also worked to promote the Anzac Centenary in his Batman electorate, and to secure grants for local projects to commemorate the service of Australian service-men and women in the First World War.

[16] Feeney sought to promote causes in parliament including recognition of same-sex marriage, needs-based school funding, and various environmental concerns, particularly marine parks and fisheries protection.

In 2017, Feeney was one of a small number of Labor MPs to express opposition to the Carmichael coal mine proposed by the Adani Group, saying the project didn't "stack up" and calling the cost to the environment and climate "too high".

[19][20] At the 2016 federal election the Australian Greens focused their campaign effort against several inner urban electorates with sitting Labor MPs, including Feeney's seat of Batman.

Feeney attracted controversy when it was revealed he had failed to disclose an investment property he owned in Northcote (valued at $2.3 million) on the Parliamentary Register of Interests.

While Feeney claimed that he had gained no financial advantage from his mistake, accusations that he had "forgotten his house" caused significant damage to his re-election campaign, which had focused on Labor's policy to abolish negative gearing.

His campaign in Batman was described by the Herald Sun as "tumultuous", with Feeney also leaving confidential Labor briefing notes in a TV studio after an interview on Sky News.

His thesis entitled Second Punic War: the contest for the central Mediterranean, Hannibal and Carthaginian grand strategy 218-210 BC won the 2020 William Culican Memorial Award.