He finished his studies without a degree and worked in the office of Christian Ströbele, member of the Bundestag for the Greens, from 2003 to 2011.

[3] The two led the coalition negotiations with the SPD under Governing Mayor Klaus Wowereit after the 2011 Berlin state election.

[4] Wesener and Jarasch were re-elected as co-leaders in March 2013, achieving an unusually broad support among delegates at the party conference.

[7] In October 2015, Wesener was nominated as part of a four-member team of lead candidates for the 2016 Berlin state election alongside Bettina Jarasch, Antje Kapek, and Ramona Pop.

[2][12] In accordance with the principle of separation of mandates, Wesener resigned from the Abgeordnetenhaus at the beginning of 2022, and was succeeded by Catrin Wahlen.