[5][4][6] In December 2017, during the parliamentary eligibility crisis, the High Court declared him elected in place of Fiona Nash, who was ineligible to stand.
On 10 November 2019, Molan was selected by the NSW Liberal Party to fill the casual vacancy left by the resignation of Senator Arthur Sinodinos.
[10] He maintained an interest in aviation and held civil commercial licences and instrument ratings for fixed and rotary wing aircraft.
[15] Molan served as the army attache in Jakarta as a colonel between 1992 and 1994 and for this service he was awarded the Indonesian decoration Bintang Dharma Yudha Nararya in 1995.
[23] The book concentrated on his experience as chief of operations in Iraq during 2004–05, and contained some criticism about Australia's capacity to engage in military conflict.
[7][33] In February 2018, it was revealed that Molan shared, on his personal Facebook page in March 2017, anti-Muslim content from the far-right political party Britain First.
[35] In response to the Facebook post, Greens MP Adam Bandt accused Molan of war crimes over his actions in Iraq, but later apologised.
[39] In November 2018, Molan polled the third-highest number of votes in the Liberal Party's Senate preselection ballot for the 2019 federal election.
Subsequently he was placed in the "unwinnable" fourth position on the coalition's Senate ticket in New South Wales, below Hollie Hughes, Andrew Bragg, and the Nationals' candidate Perin Davey.
[40] Molan was disappointed at being relegated to a low-priority position on the official Coalition NSW Senate ticket and spoke of being unable to defend the Liberal Party after the decision.
[43] However, on 10 November 2019, Molan was selected by the NSW Liberal Party to fill the casual vacancy left by the resignation of Senator Arthur Sinodinos.
He was appointed by a joint sitting of the NSW Parliament on 14 November 2019, and served the remainder of Sinodinos's six-year term, which expired in June 2022.
[46] On 5 April 2021, Molan announced that he had been diagnosed with an aggressive form of cancer, and that he would be taking leave from the Senate to undergo further testing and treatment.