He will remain as chairman of the firm, having held this and the CEO positions since 2001.
As of May, he oversaw £3.9bn funds under management, of which £2.4bn was in funds managed for Marlborough.
He remains as lead manager of the flagship £822m Marlborough Special Situations fund, as well as co-manager of the £406m UK Micro Cap Growth and £972m Multi-Cap Income funds.
Hargeaves founded Hargreave Investment Management in 1986, which merged with Hargreave Hale & Co two years later.
Hargreave said: “Our advisory business is expanding as well so it makes sense for me to remain as chairman and lead manager of our funds and relinquish the CEO duties. Hargreave Hale has built its business on putting clients first and its appropriate with the level of assets we have that I concentrate on my clients."
