Treacy made his Preston North End debut, coming on as a 56th minutes substitute, in a 4–1 loss against Barnsley on 2 February 2010. After missing two matches due to injury, he returned to the first team against Watford on 3 April 2010, coming on as a 38th minute substitute, and set up the equalising goal, in a 1–1 draw. This was followed up by scoring his first goal for the Lancashire outfit in a 3–1 defeat Crystal Palace on 5 April 2010, and another came against over Scunthorpe United five days later, as well as, setting up one of the goals, in a 3–2 win. In the second half of the season at Preston North End, Treacy scored twice in seventeen appearance. A few weeks after the 2009–10 season, he had a successful operation on his hernia.