At the 2017 general election, Falloon contested the electorate of Rangitata as a candidate for the National Party. Rangitata had been held by National since the electorate was created in 2008.[6] Falloon won the electorate, defeating Labour candidate Jo Luxton by 6,331 votes.[7] With the National Party in Opposition, Falloon was appointed as the party's spokesperson on South Island regional development during Simon Bridges' leadership, and spokesperson for biosecurity under the leadership of both Todd Muller and Judith Collins.[2]
On 20 July 2020, Falloon announced that he would not seek re-election at the 2020 general election, citing personal reasons following the suicide of a friend.[10] It was later reported that he had sent a pornographic image to a 19-year-old female university student.[11] The parents of the young woman emailed this information to prime minister Jacinda Ardern; Ardern's chief of staff notified National Party leader Judith Collins. Police investigated the matter but decided that sending the image did not meet the threshold for prosecution.[12][13] According to The New Zealand Herald, Falloon claimed that he had left his phone unattended during the party and that one of his acquaintances had sent the image. Despite insisting that he had not sent the message, Falloon reportedly offered his resignation to Collins, which she accepted.[14]
On 21 July 2020, Falloon resigned as a Member of Parliament effective immediately. His resignation accompanied media reports that he had sent two inappropriate images to two other women. Collins also stated that she "no longer trusted his story" of the incident with the first woman and "had lost confidence in him."[15][16][17] After his resignation a total of “at least five" women have reported similar behaviour by Falloon.[18][19] In response to complaints that Falloon had sent unsolicited explicit messages to multiple women, the New Zealand Police launched an investigation into the former National MP,[20] but at the conclusion of the investigation, Police decided not to press charges against him.[21]