Dr Marco Weiss was born and raised in Zug.

After studying at the law faculties of the Universities of Zurich and Geneva, he graduated in 1977 with a master's degree. This was followed by periods of professional practical training at the law courts in Zug (Cantonal Court, Supreme Court and Administrative Court). In 1979 Dr Marco Weiss was called to the bar with notarial authority. In the same year he joined the central Legal Department of Union Bank of Switzerland (UBS) in Zurich. Marco Weiss was awarded a doctorate in law by the University of Zurich for his dissertation "Das Verfahren der Verwaltungsrechtspflege im Kanton Zug" ("Administrative Law: Procedure and Practice in the Canton of Zug").

In 1986 he founded the lawyer's and notary's office in Zug, specialising in business law.