Dowler, who joined Finsbury from FTI Consulting in May 2010, will become MD, public affairs, next week.
He will be based in London and work in the global comms team alongside New York-based senior managing director in the public affairs group Peter Rose.
He has a long working relationship with the firm, having led RLM Finsbury’s account with Blackstone and previously worked with the company when it retained FTI Consulting.
Dowler and Finsbury were drafted in to help Blackstone deal with the fallout from the 2011 crisis enveloping Southern Cross Healthcare when the UK media were blaming the firm’s private equity owner for the care home operator’s demise.
It is not thought Blackstone will retain any consultancy following Dowler’s hire.
Dowler has specialised in M&A, restructuring projects and private equity deals, previously working on transactions including Terra Firma’s acquisition of EMI and ABN Amro’s sale to Royal Bank of Scotland.
Blackstone is the world's largest alternative asset manager and in the UK holds stakes in Merlin Entertainments (the owner of the London Eye and Madame Tussauds and a strongly tipped IPO candidate) Cineworld and United Biscuits.