He appeared in the 2016 Summer Olympics and remains the first and only German footballer who has scored five goals in a single game with the national team.

[6] In future matches, he would serve as a "super-sub" coming off the bench to score decisive goals against Alemannia Aachen, Erzgebirge Aue, 1.

After the winter break, his playing time increased as he was able to score nine goals in 14 appearances, securing his place in the starting line-up.

[11] Nils Petersen scored his first hat-trick (three goals) in the first ever game he played for FC Bayern Munich against a Trentino Selection.

On 29 June 2012, SV Werder Bremen agreed to a one-year loan deal with Bayern Munich for Petersen.

[14] On 31 January 2015, in his league debut versus Eintracht Frankfurt, he scored a hat-trick, despite just coming on as a substitute for the second half, ultimately helping his team turning a 0–1 deficit into a 4–1 victory.

[19] On 9 August 2015, he continued his good form by scoring his second hat-trick in three games, in a 5–0 win at fifth-tier side HSV Barmbek-Uhlenhorst in the first round of the DFB-Pokal.

[21] Petersen made his 100th top flight appearance on 29 October 2016 by coming on in the second half of the 3–1 away win against his former side Werder Bremen.

[23] In the 2017–18 season, Petersen was the top scoring German in the Bundesliga with 15 goals, finishing second to only Robert Lewandowski of Bayern Munich.

On 19 January 2019, he scored his 38th league goal for Freiburg, breaking the club's all-time Bundesliga goalscoring record previously held by Papiss Cissé.

[34] Petersen was then handed his first cap in a friendly versus Austria on 2 June in preparation for the World Cup,[35] but was left off of Löw's final squad for the tournament.