The 99-time Blues' pivot played 44 Tests for the All Blacks and 89 games for Auckland during his career spanning the turn of the century. He also played for Northampton and Gloucester in the English Premiership.
Since building his coaching record after completing his rugby-playing career in South Africa in Gauteng, he has coached in the Republic, the United States and the Hurricanes in Wellington.
Now he has taken the chance to join head coach Willie Walker and fellow assistant coach Linda Itunu with the Blues.
Spencer, 47, said: "When I was playing, I always liked to bring a bit of innovation and 'out-of-the-box' thinking to the table. Now, as a coach, I want to encourage and help grow those same traits in our Blues wahine."
Like most of New Zealand, he was caught up in the Black Ferns' World Cup success, and he anticipates there will be a follow-on effect in Sky Super Rugby Aupiki.
"You've seen the rise of women's rugby and the way the public got right in behind the Black Ferns.
"We're at an exciting juncture for the sport, and I'm looking forward to getting involved and doing what I can to help grow and support women's rugby."
"I've known Willie [Walker] for a while. We've thrown the touch ball around and have a good relationship. He's done some fantastic work with the Auckland Storm in the Farah Palmer Cup, and I'm looking forward to exchanging ideas and getting the backline humming.
"I don't know Linda, but have seen her exploits on the field for many years with the Black Ferns – she was an enforcer on the field,"
Blues chief executive Andrew Hore said having Spencer on board with the Blues organisation was special, and was an example of harnessing the resources available within the franchise's region.