Cartwright, who spent almost 10 years at Ketchum before stepping down earlier this year, starts at Text100 later this month, reporting to agency CEO Aedhmar Hynes.
He succeeds Cecile Missildine, who has been appointed as head of Text100's global insights and analytics unit, following five years in the EMEA role.
Cartwright will be responsible for Text100's EMEA offices in the UK, France, Germany, Spain, Italy, Sweden and the Netherlands, leading a team of approximately 200.
Key clients in the region include Vodafone, IBM, Coca-Cola, Facebook and Pizza Hut, Text100 said.
During the summer it was revealed consumer agency Lexis was merging into Text100, making the tech-focused agency's London office its largest location globally.
Prior to joining Ketchum in 2008, Cartwright was director of public affairs at Hill+Knowlton, and before this was director and head of public affairs at IT services provider GCI London.
Cartwright, who is also a mentor on the PRWeek-PRCA fast track mentoring scheme, started his career in PR as an intern at PS Public Affairs in 1994, his LinkedIn profile states.