He was a boarding student with professors P. Farreras Valentí, A. Pedro Pons and S. Woessner. He worked for 20 years under the direction of Professors Ciril Rozman and Joan Lluís Vives Corrons. In 1975-76 and 1981-82 he made research stays at the University of Paris (Beaujon Hospital) and at Harvard University (Massachusetts General Hospital).

He was Head of the Hematology Service at the Germans Trias i Pujol University Hospital - HGTiP (1991-1995), Medical Director of the HGTiP (1995-97) and Managing Director of the same center (1997-2002). He has been Center Director of the Catalan Institute of Oncology (ICO) (2003-2009), Scientific Director of the ICO, Director of the University Relations Program and Head of the Hematology-Laboratory Service of the ICO-Badalona until 2018. He is currently an honorary consultant of the ICO. He was tenured Professor of Medicine at UB and UAB (1985-1997 and 1997-2007, respectively) and, Professor of Medicine-Hematology at UAB from 2008 to 2018. From 2018 to 2021 he was Professor Emeritus of the UAB and from 2021 to the present day he is Honorary Professor of the same university.

He is Trustee and Scientific Director of the Josep Carreras Leukaemia Foundation, founding member and president of the Management Committee of the Josep Carreras Leukaemia Research Institute, vice-president of the Josep Carreras Foundation, Numerary Academician of the Royal Academy of Medicine of Catalonia and Doctor "Honoris Causa" by the University of Asunción.

Prof. Feliu is a prestigious researcher in the field of procedures and integrated methods of hematological diagnosis, especially electron microscopy of blood and bone marrow cells and in the study of spleen pathology, with relevant contributions in these areas at national and international level.

He has collaborated in the writing of 85 books and has published 386 articles, half of them in international journals, with an h-factor of 33.

He has held executive positions in the journal Medicina Clínica, the Spanish version of the journal JAMA, the Tratado de Medicina Interna Farreras-Rozman, and the book: Semiología y Métodos de Exploración en Medicina.