Waters, 29, joins Welsh after three seasons at the Dragons. The openside flanker came to the attention of the Dragons after joining Pontypridd in 2009, initially on trial.
His impressive performances over the next two seasons, which included scoring 11 tries, earned him a professional contract with the region.
He made his debut for the Dragons as a replacement versus Aironi at Rodney Parade in September 2011. His first start came in the LV= Cup against Bath.
Waters started against Welsh in the Dragons’ LV= Cup victory over the Exiles at the Kassam Stadium in February 2013.
London Welsh head coach Justin Burnell said: “I’ve known Darren for a long time, going back to watching him during his time at Pontypridd and then at the Dragons, and he’s a sheer raw talent.
“He’s phenomenal at the breakdown, one of the best I’ve seen, and he has an abundance of energy. He’s going to be an absolutely fantastic asset and a really positive addition to our environment.”
The 2014/15 Premiership season will see Sunday afternoons at the Kassam Stadium in Oxford (kick-off 2:30pm) become synonymous with London Welsh (unless on occasions when dictated otherwise by television), with the club having committed to playing its home games at the Kassam Stadium for the next three years.
