The 44-year-old is looking forward to linking up with new Director of Rugby Dean Ryan and also thanked London Wasps and Dai Young for their understanding and support.
Howarth said: "It's a very exciting challenge to be joining Warriors under the new leadership of Dean.
"When I joined Wasps they were not in a great position after what had been a difficult year. But we encouraged the team to play and the young talent has really stepped up this season.
"Warriors are now looking to bring young emerging talent to the fore and that is what I want to help achieve.
"There is a huge amount of talented young rugby players in England at the moment," he added.
"I've been stunned by the depth and it's clearly not just in New Zealand where exciting young players are being developed. I want to see that happening at Warriors.
"I would like to go on record to personally thank London Wasps for their understanding and especially Dai Young for the opportunity he gave me. My family are a big part of this decision process, having not settled in London, and we are looking forward to the move to the Midlands."
Howarth was a full-back for Sale and Newport during his playing days and won four New Zealand caps in 1994.
Under the International Rugby Board rules of the time he went on to play for Wales, making his debut against South Africa in 1998 and going on to win 19 caps.
He has made his name in coaching since hanging up his boots and is looking forward to his next challenge at Warriors alongside Ryan.
"The chance to work with Dean is a big incentive," he added. "I played against him as a player and he is a straight up and down character. He has a quality rugby brain and I look forward to now teaming up with him at Sixways."