Ranieri has taken full ownership of the French agency, which is projected to take revenues of €800,000 (£672,000) this year. The fee paid was not disclosed.
Ranieri's parent firm Vodrum was last year acquired by The Marketing Group – a fast-growing network founded by a private equity veteran – which now owns 17 agencies.
Founded in 1999, Reflexion Publique's clients include Olympus, UBTech and Blue Microphones. MD Franck Ambre remains with the business under its new ownership.
Ranieri had worked with the Paris firm for around a decade as a partner, with shared clients including headphones maker AfterShokz, audio equipment firm Libratone and laptop and tablet maker Venturer; the latter having been rolled out into France after first working with Ranieri in the UK.
Its founder Pietro Ranieri said: "Our clients are increasingly looking for us to manage European-wide communications campaigns and Reflexion’s reputation in France is unsurpassed in the consumer technology space. We know Reflexion well and the team has the same feel and tailored approach to the communications mix that we have here at Ranieri."
Ranieri created his agency in 2002. It now has 17 staff and grew revenues by a third to £1.2m last year.