[10] Campion played with amateur USL Premier Development League sides Baton Rouge Capitals and Ventura County Fusion while in college.
[15][16] Campion signed with Swedish Division 1 side Norrby IF in 2013 after leaving UC Santa Barbara and made his debut on 21 April 2014, scoring in extra time.
[29] After the game Page defended his decision to restrict Campion's playing time despite his success at reserve level, saying he did not want to "throw him in the deep end straight away".
[31] He began training with National League side Torquay United on 22 October,[32] and agreed a one-month loan deal with the club seven days later after "Gulls" manager Kevin Nicholson was impressed by his character.
[36] Chairman Norman Smurthwaite used Twitter to express his view that Campion had been treated unfairly by former manager Page and said he hoped to bring the striker back for pre-season.
[40] He scored two goals in 23 appearances across the 2017 season, helping the "Rebel Army" to win both the Premier Division title and the President of Ireland's Cup, though he was an unused substitute in the final at Turners Cross.
[41][42][43] On 4 November, he entered the final of the FAI Cup at the Aviva Stadium as a substitute in extra time, and went on to score the equalising goal of a 1–1 draw; Cork went on to win the trophy on penalties.
[44] On 2 January 2018, Campion joined NIFL Premiership club Linfield on loan for the rest of the 2017–18 season; manager David Healy said "he's a player we know well and have seen play live several times".
[47] In September 2014, the Port Vale website described him as "a strong target man, who is good at holding up the ball, can finish well when given the opportunity, and due to his size is also an aerial threat".