De Wynter left Tequila in October after almost a year with the agency, was previously deputy managing director at Mook and has 12 years' digital experience under his belt. He has worked on projects for brands including T-Mobile, Vodafone, Pedigree and Peroni.
De Wynter also spent a year and a half working for Mars, as a digital strategist and senior account manager for the launch of Mars.com and the dotMars global intranet.
Gail Dudleston, Twentysix's chief executive, said: "Lex has a deep understanding of technologies across the digital media mix, with a particular focus on web and mobile, as well as the social and user trends that define their development.
"He also possesses talent and vision that will benefit our clients and our organisation and we are delighted to welcome him."