[13] Borysiewicz pursued a career in academic medicine at the University of Cambridge, where he was a fellow of Wolfson College, and then as a consultant at Hammersmith Hospital.

He headed the Department of Medicine at the University of Wales before joining Imperial College London, where he was promoted to Deputy Rector responsible "for the overall academic and scientific direction of the College,"[14] In September 2007, it was reported he would succeed Colin Blakemore as the 9th head of the Medical Research Council, a national organisation that supports medical science with an annual budget of around £500 million.

Cancer Research UK is one of the world's largest fundraising charities and is governed by a council of trustees, led by Borysiewicz.

The council's role is to set the charity's strategic direction, uphold its value and governance, and guide, advise and support the chief executive.

He was also a Governor of the Wellcome Trust, a founding Fellow of the Academy of Medical Sciences (FMedSci)[35] and co-chair of the MRC's advisory group on stem cell research.

[39] Also in this year, he was honoured with an honorary Doctor of Science degree (Hon DSc) by the University of Exeter for his contribution to medicine and medical research.

[41] In 2012, Borysiewicz was awarded the honorary degree of Doctor of Science honoris causa (DSc h.c) by the University of Hong Kong in recognition of his contributions to medical research and society.