He qualified for the 2015 UK Open in 56th on the UK Open order of merit so started in the second round. He beat Matt Pagget 5–0 in the second round but lost 6–9 to Dave Chisnall in the third round. He qualified for the 2016 UK Open where he reached the last 64 again after wins over Glen McGrandle and Darron Brown, before losing to eventual winner Michael van Gerwen. Harrington got a Tour Card after he finished fourth in the UK Q School Order of Merit in January 2018.