Kenny Shiels the League Cup Final, where they upset the odds by beating Celtic 1–0, with Dieter van Tornhout scoring the crucial goal in the 83rd minute. Killie's joy was tempered by the death of Liam Kelly's father, Jack, who suffered a fatal heart attack at the final whistle of the game. On the win, Shiels stated the team "are thinking more about Liam (Kelly) than our triumphalism". He then told BBC Scotland's Jonathan Sutherland, winning the cup is "unbelievable", in addition "a great emotion" for the Kilmarnock's supporters. Following his side's historic cup win, Shiels announced his intention to stay at
Dean Shiels to join Rangers. He scored a goal, as well as, setting up two goals in his first appearance, in a Scottish League Cup tie against East Fife on 7 August. A week after he sustained an injury during a match which ruled him out for weeks, On 2 September 2012, Shiels scored his first league goal, as well as setting up a goal, in a 5–1 win over Elgin City. After scoring two goals in three games, Shiels scored against the Scottish Premier League side Motherwell, in a Scottish League Cup tie. Then, in the Scottish Cup, Shiels scored twice