On 12 August 2012, Lewandowski began the 2012–13 season by scoring in the 1–2 2012 DFL-Supercup defeat to Bayern Munich. He made his first appearance of the 2012–13 Bundesliga campaign in Dortmund's 2–1 victory over Werder Bremen on the opening day of the season. He netted his first goal in the 3–0 victory over Bayer Leverkusen on 15 September 2012, extending Dortmund's run to 31 games unbeaten and moved the club into third in the Bundesliga. Three days later, in the club's first Champions League game of the season, Lewandowski netted an emphatic 87th-minute winner to defeat Ajax by a score of 1–0. He set club's new record of the longest scoring streak, having scored in 12 consecutive league games, surpassing Friedhelm Konietzka's record from 1964–65 season. On 9 February 2013, Lewandowski opened the scoring in a home match against Hamburg, but was sent off in the 31st minute for a foul on Per Ciljan Skjelbred and Dortmund lost 1–4. He finished season with 24 league goals, one goal short of the Bundesliga's top scorer, Bayer Leverkusen's Stefan Kießling.