The dynamic and versatile back, equally comfortable at full back or fly half, has played for the Chiefs in the Super 14 competition and Waikato in the Air New Zealand Cup. He also recently enjoyed a successful spell at Guinness Premiership side Newcastle Falcons.
Crichton has also impressed on the international stage since making his Samoa debut in 2006, during the inaugural Pacific Five Nations tournament. He was named in the Pacific Islanders touring squad in 2006 and is currently in action in the iRB Pacific Nations Cup for Samoa.
"Loki is a very talented international player and as such he will bring a huge amount of experience to the Warriors," said Director of Rugby Mike Ruddock. "He can play in more than one position and with a demanding season ahead of us he will give us lots of selection options. Loki has a good all-round game with tackling and passing of the highest quality.
"When he played against the Warriors last season he got his back line working very well, particularly in the first half when Newcastle had the ball. Thankfully the Warriors turned the game around in the second half and starved Newcastle of possession. However, Loki showed on that day what he was capable of when given the platform."
Crichton, who joins Sam Tuitupou, Greg Rawlinson and Sean Ruwers as the new arrivals at Sixways, added: "I'm delighted to sign and already looking forward to meeting up with my new team-mates and joining the Warriors family.
"I was very impressed with Mike (Ruddock) and how he wants to play the game, I know that will suit my style. Worcester plan to play some great attacking rugby in the coming season and that is the way I like to play.
"I've already tasted the wonderful atmosphere at Sixways during my time with Newcastle and know the facilities off the pitch are first rate and will only get better in the coming years. The supporters at Worcester also have a wonderful reputation in the English game and I plan to be key part of a team that will play a brand of rugby that those fans will relish watching.
"The club has a vision for the future to become the very best in European rugby - I want to be a big part of that journey."
* Season tickets are available NOW from Sixways. For more information call the ticket office on 0870 990 5650. Existing season ticket holders have until June 8 to renew to take advantage of the special discounted rate and get first refusal on their existing seat.