Mr Beer, formerly managing director of investment solutions and distribution, replaces retiring chief executive David Nicol.
The move was announced in January.
Brewin has an expanding Financial Planning presence with Financial Planning income growing rapidly in recent years.
The company employs more than 105 qualified Financial Planners and 129 Paraplanners and assistants.
Last year the company acquired Bath-based Epoch Wealth Management LLP, an independent Financial Planning firm with 38 members of staff.
Mr Nicol decided to retire after eight years with the group, the company announced in January. He will remain with the company until the end of July to hand over the ropes to Mr Beer.
Mr Beer was previously responsible for Brewin Dolphin's intermediaries, charity, professional services and digital businesses. He has over 20 years of experience in financial services, previously working at National Australia Bank, Gerrard and Barclays.
He joined Brewin Dolphin in 2008 to open and run the Nottingham office. He then became regional director in the Midlands, before taking charge of the intermediaries' business in 2013 which expanded funds under management to over £14bn.
He joined the executive committee in 2016, with further responsibilities for research, investment governance and the development of investment solutions.
Earlier this year Mr Beer said: "I am delighted to be chosen to lead the business at this juncture and I look forward to continuing to build on David's achievements to drive the business through its next phase of development."