With a client roster that includes CFOs, board members and senior managers, Rosinus Partner offers vast knowledge of tax, antitrust, fraud and money laundering offences as part of a busy workload, which also extends to instructions related to regulatory offence proceedings. Frequently leading the firm’s cross-border mandates, Christian Rosinus co-heads the firm alongside Mathias Grzesiek, who is a key contact for the firm’s healthcare clients and is well versed in IT criminal law. Arthur Leonhardt joined the team from Clifford Chance in April 2025, further strengthening the team’s capabilities in foreign trade and sanctions law. Janina Brandau departed in March 2025, while Mirjam Steinfeld was promoted to partner in July 2025.
Legal 500 Editorial commentary
Accolades
Client satisfaction: Lawyer & team quality
Testimonials
Collated independently by Legal 500 research team.
- 'A quiet hero.'
- 'The team reacts extremely quickly and is very sensitive to the needs and specifics of the client and the individual case. It is always enriching to work with them and to benefit from their extensive international network and outstanding expertise.'
- 'The work of Rosinus Partners has been significantly shaped by Christian Rosinus and Mathias Grzesiek. With Mirjam Steinfeld as the third partner, they have perfectly complemented their skills, market presence, and diversity.'
- 'A very good team with whom collaboration is very pleasant.'
- 'Mathias Grzesiek – clear, strategic communication, business-oriented, and pragmatic in complex situations.'
- 'Mirjam impressed us with her comprehensive knowledge, her quick responsiveness, her commitment, her remarkable self-confidence, and her strong presence.'
- 'Christian Rosinus – a brilliant advisor and a first-class criminal defense attorney.'
- 'We received the utmost attention from the top partners. The advice we received from them was excellent, and the result was the best possible.'
- 'Efficient interdisciplinary collaboration within the firm.'
Lawyers
Leading partners
The strongest partners in their field, leading on market-leading deals and endorsed by peers and clients alike.
Practice head
Christian Rosinus; Mathias Grzesiek
Other key lawyers
Mirjam Steinfeld; Arthur Leonhard