The bank, which has a history dating back to 1786, has charged Maitland with building its reputation among the national and investment press, and broadcast media.
The agency picked up the brief via a competitive pitch. It is understood that the incumbent agency was investment PR specialist Phoenix Financial PR.
Maitland will report dirrectly to Sally Tennant, formerly of Swiss private bank Lombard Odier Darier Hentsch, who joined Kleinwort Benson as chief executive in January this year.
It is thought that the bank is keen to grow its association with entrepreneurs and promote itself as a partner through the life cycle of entrepreneurial businesses - from establishment and growth through to a sale or IPO and then working with the wealth that business has created.
William Clutterbuck, head of Maitland's financial services team, will lead the account alongside Andrea Coleman and Daniel Yea.
The bank has reorganised its senior team with a number of hires since Tennant's appointment and the purchase and integration of Close Offshore Group, which grew its private wealth assets under management by £1.6bn.
The private banking industry has continued to perform relatively well despite the global banking crisis. Kleinwort Benson was rated as the top performing wealth manager in the Financial Times Private Client Wealth Management Survey 2010.
The bank has experienced ownership volatility in recent years.
It was bought by Dresdner Bank in 1995, creating Dresdner Kleinwort Benson.
Dresdner AG was then sold to Commerzbank in 2009 before Commerzbank was forced to divest the business later that year, selling it to RHJ International.