Rowntree will begin at the firm in mid-October and joins from his position as MD, corporate banking at Numis Securities.
He has worked in investment banking for 27 years including senior roles at HSBC and Hoare Govett.
The appointment comes following MHP’s parent company Engine’s acquisition by Lake Capital.
Chief executive of MHP Financial Andrew Jaques said: "Tim is quite simply a great hire for MHP. He is well known to me and the team here and we are thrilled he is joining us.
"His capital markets experience, advisory skills and deep client relationships will be invaluable as we develop our business in a period of increased M&A and IPO activity. Momentum within MHP is strong and Lake Capital brings the investment required to grow the business organically."
Rowntree added: "It's time for a change. I'm really looking forward to working with some talented people at MHP. It's a great opportunity for me to join a team with a strong and growing reputation and a business with huge potential."