The firm was created in the year 1963 by Heinz Kosesnik-Wehrle.
From 1972, his wife, Roswitha Kosesnik-Wehrle, began working at the firm.
When it became clear that the two daughters of Heinz and Roswitha Kosesnik-Wehrle would follow their parents' professional footsteps they too joined the firm. The strategic goal of the firm has been to recruit the majority of the lawyers from the family in order to ensure a certain continuity of service to the firm's clients.

In 1995, Susanne Kosesnik-Wehrle, LL. M. (Bruges) joined the firm, and her spouse, Stefan Langer - who was admitted to the Vienna bar in January 1997 - followed in 1996. Anne Marie Kosesnik-Wehrle became an associate at the firm in 1997. Mehmet Munar joined in 2007. Martin Honemann joined the firm in 2001, and received his licence to practise as a lawyer in January 2006. He is working independently in cooperation with Kosesnik-Wehrle & Langer.
From time to time, apprentice judges are seconded to the firm as part of their training.

Since 1988, the firm's offices have been located on the second floor of a "Biedermeier" style house at Oelzeltgasse 4 (close to the underground station U4-Stadtpark). In 2001, Heinz Kosesnik-Wehrle and Stefan Langer merged their practices to become the founding partners of Kosesnik-Wehrle & Langer.
In January 2003 the firm became a limited registered partnership (Kommanditerwerbsgesellschaft) under the name of Kosesnik-Wehrle & Langer Rechtsanwälte KEG (today "KG") when Anne Marie Kosesnik-Wehrle was admitted to the Vienna bar and became a further general partner of the firm while Susanne Kosesnik-Wehrle became the firm's first limited partner. Heinz and Roswitha Kosesnik-Wehrle retired in April 2003