The 30-year-old joins the Men of Gwent after nine years and over 150 appearances for Scarlets, where he was a key member of the 2017 league winning side.
Evans made his international debut against Ireland in 2015 and has gone on to earn 39 caps for his country, including starting in four games in the 2019 Grand Slam campaign.
A modern, mobile front-rower with slick handling skills, Evans will add experience and power to the front row resources at Dragons.
Director of Dragons Rugby Dean Ryan said: “We’re delighted to be welcoming a player of Rob’s calibre to Dragons and excited about the impact he can make with us.
“Rob is highly driven and motivated to help us move forward as a squad.
“He also still has big international ambitions with Wales that he wants to achieve as a Dragon.”
Evans said: “I’m happy to be joining and excited to get going next year.
“It feels like the right time for a change and, with the other signings and what Dean wants to build here, it will be brilliant and I’m looking forward to it.
“I love playing at Rodney Parade and the fans are really loud and intimidating. I’m looking forward to being a part of it and having them on my side.”
