Mike Bottjer has been Interserve's chairman for six years and chief executive for eight.
He said a chief executive would be appointed by the end of the year, adding that the group would appoint more independent non-executive directors to the main board. At present, Interserve has eight executive and three non-executive directors.
Bottjer made the announcement at Interserve's annual meeting last week. He said results for the first three months of the year had shown a "satisfactory" advance on the same period in 2001.
In the year to 31 December 2001 Interserve made a pre-tax profit of £53.6m on turnover of £1.3bn. The group employs more than 12,500 people and operates in Australasia, Asia, Europe, and South America.