Scotland midfielder Fletcher spent 12 years with Manchester United before opting to leave the club due to a lack of first-team football.
Fletcher sealed a move to The Hawthorns after a switch to West Ham fell through and the 31-year-old was influenced by his former boss Ferguson when making his decision.
He said: "Yes, I spoke to him, why wouldn't you? When I was making my decision, I bounced a few things off him,
"When someone has been such an influence on you and has given you great advice on and off the pitch all through your career you have to use these people.
"We had a fantastic chat and I know he has great relationship with Tony Pulis, as he has with lots of managers throughout the league.
"He didn't necessarily recommend Albion but we spoke about the pros and cons of different clubs around country and he couldn't speak highly enough of Albion.
"I've spoken before about him in these situations, not only from a football point of view but a personal point of view and how he cared for me more in that situation than actual football side of things and that speaks volumes about him."
Fletcher could make his Albion debut in Sunday's Premier League clash at Burnley.
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