He made 104 appearances for Sale, scoring one try, during his six seasons at the club, before leaving in 2011 to join French Pro2 side Bourgoin.
Briggs began his professional career at Rotherham in 2004, where he spent time at flanker, wing and even at full-back, before making the number two jersey his own.
He represented England at Under-21 and was selected in England's squad for the Under 21 World Cup finals in Argentina in 2005. He toured with the England Saxons in 2009 in the Churchill Cup and made his Saxons debut in a 28-20 win over Argentina A in Denver.
"It's going to be a big challenge, but I like that," said Briggs. "It's a chance to help a club grow. London Welsh is a club which wants to push forward and they showed that with the fight they put in to go up. I'd heard good things about Lyn [Jones] and they play some pretty attractive rugby.
"The Premiership's tough for teams who've been there for ten years, so for a team coming up it's always going to be hard, but having seen how hard the boys are working and the way they want to play, I think we'll surprise a few people.
"Bourgoin was amazing, I loved it. I was made to feel very welcome and it was a great experience. Being in a different culture and learning a new language has helped me to grow and I think that will help me back in the Premiership, and in turn London Welsh."
London Welsh head coach Lyn Jones added: "Neil is a very experienced campaigner. He's got a lot of qualities and he'll add some stiff competition in the hooker position."