Treacy returned to Ireland and joined struggling Premier Division side Drogheda United midway through the season. He made his debut for the club, starting a match and played 64 minutes before being substituted, in a 4–1 loss against Limerick on 28 August 2015. It wasn’t until on 25 September 2015 when Treacy scored his first goal for Drogheda United, in a 2–2 draw against Bohemian. This was followed up by scoring his second goal for the club, in a 1–1 draw against Cork City. However, his two goals in eight games was not enough to help his side avoid being relegated on the final day of the season.