Weimer studied economics, business administration and geography in Tübingen and St. Gallen and did his doctorate at the University of Bonn. After his time at the university, Weimer, who was born in Wertheim, worked for the management consultants McKinsey and Bain. In 2001, he joined Goldman Sachs as Managing Director and later became Investment Banking Partner there. In 2007, Weimer joined the UniCredit Group as Head of Global Investment Banking in Munich. In 2009, he was appointed Spokesman of the Management Board of HypoVereinsbank (today UniCredit Bank AG). In this function, Weimer also belongs to the Executive Management Committee of the UniCredit Group.