After graduation Heymans worked at the Collège de France (under Prof. E. Gley), the University of Lausanne (under Prof. M. Arthus), the University of Vienna (under Prof. H. H. Meyer), University College London (under Prof. E. H. Starling) and Case Western Reserve University School of Medicine (under Prof. C. F. Wiggers).
Efter endt uddannelse arbejdede Heymans på Collège de France (under Prof. E. Gley), Université de Lausanne (under Prof. M. Arthus), Wien Universitet (under Professor H. H. Meyer), University College London (under Prof. E. H. Stær) og Case Western Reserve University School of Medicine (under Prof. C. F. Wiggers).