The Ospreys have completed the signing of former All Black Justin Marshall on Tuesday on a two-year contract.
Marshall asked for a transfer when the Tykes' drop was confirmed
The 32-year-old arrives in Wales from Leeds, after the Tykes were relegated from the English Premiership.
Marshall, who won 81 New Zealand caps, is believed to have rejected an offer from Wasps in favour of the Ospreys.
"The Ospreys are a team who are going places and I have been very impressed with their professionalism on and off the pitch," Marshall said.
This season the Welsh regional side have taken up residence at the new 20,000-seat Liberty Stadium, which they share with football team Swansea City.
Last week a new Celtic League regular season record 15,183 fans turned up to see the Ospreys beat Welsh rivals Llanelli Scarlets 25-13.
"They have a magnificent stadium, some of the best training facilities I've seen and a squad that I believe can compete with the best in Europe," Marshall added.
"I have recently visited south Wales with my wife and we are both looking forward to bringing our young family down to settle in the area."
As well as Wasps, Marshall had also been linked with moves to newly promoted Harlequins and French club Bourgoin.
"I was approached by clubs from England and France but I have been motivated by the Ospreys' ambitions," Marshall said.
"Once I had spoken to the Ospreys and seen the area and set-up with my own eyes, it was a simple decision in the end."
Marshall may not be the only new Kiwi recruit to sign for the Swansea-based team, as Waikato and Chiefs back-row Jono Gibbes is also thought to be close to joining.
Gibbes, 29, has won eight caps for New Zealand - his last against the British and Irish Lions last summer - but has fallen down the All Blacks pecking order after two injury-disrupted seasons.
Another back-row target is Filogia Tiatia, a former star with Wellington and the Hurricanes who has two All Blacks caps.
The 34-year-old has recently been playing his club rugby in Japan for Toyota Verblitz.
There is already a strong Kiwi influence within the Ospreys squad, with Jason Spice, Adrian Cashmore and Damian Karauna currently at the Liberty Stadium.
Spice is the incumbent at scrum-half and will contest the number nine shirt with Marshall.
The Daily Mail claimed that Wasps were prepared to pay Marshall around a third of the £160,000 a year he received at Leeds.
Wasps chief executive David Davies said of their failed swoop: "We did our best but it wasn't to be."
Marshall had a year to run on his two-year deal at Leeds but asked to be released after their relegation was confirmed earlier this month.
That could mean the Ospreys having to pay a transfer fee on top of Marshall's wages, meaning some cost-cutting elsewhere in the squad.
The Kiwi joined the Tykes at the start of last season.
"I have enjoyed my experience at Leeds immensely this year and I would like to thank the players, coaches and supporters for the way in which they have welcomed me and supported me throughout the season," Marshall said.
"I sincerely wish them a swift return to the Guinness Premiership next season.
"But I am a very ambitious, competitive individual and I look forward to furthering my ambitions with the Ospreys."