Most recently Beales worked as a senior director at WPP, prior to which he was executive director at the Labour Party, responsible for strategy and planning, from 2010 to 2015. He was a senior advisor in Downing Street between 2006 and 2010.
Beales was also national performance director for the NHS, where he focused on reducing waiting times for treatment and improving hospital cleanliness. In addition, he has worked on the development of the Living Wage campaign.
His predecessor, Roger Harding, has moved to social research institute NatCen to become head of public attitudes.
Beales reports to CEO Polly Neate, who joined in August.
Beales said: "In the aftermath of the dreadful loss of life at Grenfell Tower, it has never been more important that the voices of those who live in social housing and who need social housing are heard. It is a particular responsibility to be joining Shelter at this time and I look forward to helping to make the case for better treatment for those who rent and more safe, high-quality and affordable social housing which our country so desperately needs."