Non-League Muldoon started his career at home-town club
Scunthorpe United as a
winger, being released in his second year as a youth. After a mid-season at
Doncaster Rovers he moved to lower league football, starting with
Brigg Town. Muldoon subsequently represented
Sheffield,
Glapwell,
Alfreton Town,
Stocksbridge Park Steels,
North Ferriby United and
Worksop Town. With the latter he scored 21 league goals during the campaign, attracting interest from
Football League clubs.
Rochdale On 15 May 2014, Muldoon joined
Rochdale on a one-year deal, and then quit his job as a plasterer in order to pursue being a professional footballer. He made his début on 7 October 2014, coming on as a 58th-minute substitute during Rochdale's 1–0
Football League Trophy defeat against
Walsall. He made his Football League debut on 15 November 2014, coming on as a 68th minute substitution for Michael Rose in a 0–1 away loss against
Port Vale. He was released at the end of the season.
Lincoln City On 28 May 2015, he signed an initial one-year contract at
Lincoln City after his release from
Rochdale. Made his debut in a 1–1 home draw with
Cheltenham and then managed to score his first goal for the Imps in a 1–1 draw with
Eastleigh. In January 2016 he signed a new one-year contract extension.
Harrogate Town On 30 June 2018, Muldoon signed for
Harrogate Town from
AFC Fylde. Muldoon played in and won the 2020 FA Trophy final with Harrogate. ==Personal life==