The 24 year-old has represented Wales at Under 18, 19 and 20 age grade and was the top try scorer in the Wales Under 19 Grand Slam side in 2006.
A big abrasive and dynamic scrum half Lewis stands at 6'2" tall and weighs 92kgs. Lewis started his career at the Dragons where he came through the Academy system before going on to make 17 appearances for the senior side including four Heineken Cup matches.
He then moved on to London welsh where he made 80 appearances and was an integral part of the team that were promoted to the Premiership this season.
Speaking of the signing Cardiff Blues Director of Rugby, Phil Davies said,
"We welcome Rob Lewis to the Cardiff Blues and he will provide us with more options at scrum half."
"He is an exiting young player and joins us following a successful season with London Welsh."