His first goal of the season came in Leverkusen's opening match of the Bundesliga campaign on 25 August 2012, netting the opener as his side fell to a 2–1 defeat to Eintracht Frankfurt. Kießling scored his only goal of Leverkusen's Europa League campaign on 4 October, coming on as a substitute and scoring the winning goal away to Norwegian side Rosenborg BK. On 15 December, Kießling scored a brace to keep Bayer close on the heels of Bayern Munich heading into the winter break; the goals also meant that at mid-season he was the top scorer in the Bundesliga. In PowerTable Sports Bundesliga XI of the Season, created at the mid-way point of the campaign, Kießling was the only striker included in a 4–2–3–1 formation.