In 1974 Paul was appointed to a Lectureship in Systems and Mechanics and then in Water Resources Systems Engineering in 1977.  In 1987 he was appointed to the Chair of Civil Engineering Systems at Heriot Watt University, becoming Head of the Civil Engineering Department in 1989 and then Head of the combined Department of Civil and Offshore Engineering from 1991 to 1999.

Between 1999 and 2014 he was Executive Director of the Scottish Institute of Sustainable Technology (SISTech) Ltd, a Heriot Watt University/MWH joint venture spinout company providing research-led consultancy and innovative solutions in sustainable development in the natural and built environments.

He was the 145th Past President (2009-10) of the Institution of Civil Engineers,  is a Fellow of the Royal Society of Edinburgh and a Fellow of the Royal Academy of Engineering. He is President of the Commonwealth Engineers Council. He was awarded the CBE for services to technology in the 2011 Queen's Birthday Honours List.

Paul Jowitt was a Board Member of Scottish Water from 2002-2008, and a non-Executive Director of United Utilities Water from 2009-2011. He is Chairman of the charity Engineers Against Poverty. He is also a Trustee of The Steamship Sir Walter Scott Trust.