Ferguson, who scored 72 goals in 273 appearances for Everton, has been promoted to Martinez's first-team coaching staff on a permanent basis.
The 42-year-old former Scotland international has spent the last two and a half years working with the club's under-18s, while his role this season has also included one day a week with the first team.
Manager Martinez said: "He's developing into a really exciting coach. He's been a big influence in the work he's done with the under-18s and I do feel we need his influence in the first-team environment.
"He's an Evertonian and he's going to be a big part of the first-team staff from now until the end of the season.
"His development as a coach has really impressed me and I think he will become someone very special in that first-team structure. The players respect him and we're going to get a lot out of his work."
Ferguson's reputation on the pitch was as a hard man rather than a student of the game, but Martinez has been hugely impressed by his development as a coach.
"Duncan is really taking that role with real desire and he's someone that can achieve as much as he wants in that area," he said of Ferguson's future prospects in management.
"I've seen a huge difference from the beginning of the season until now."
Ferguson described the opportunity as "a dream come true", telling evertonfc.com: "Everyone knows what this club and the supporters mean to me and if the manager thinks I can make a contribution then I am delighted to do so. There's a lot to play for this season, it's exciting times and I am made up to be a part of it."
Everton return to Barclays Premier League action with a trip to table-toppers Chelsea on Saturday after reaching the quarter-finals of the FA Cup with victory over Swansea last weekend.
The Toffees badly need a result at Stamford Bridge after slipping eight points behind Liverpool in the race for fourth place, albeit with a game in hand on their city rivals and fifth-placed Tottenham.
Liverpool are only one point adrift of Manchester City in third and four behind Chelsea but Martinez sees the title race as being between Jose Mourinho's side, City and second-placed Arsenal.
He said: "When you've got one team with a large difference of points, you can easily overcome that, but when you've got three teams in the final third of the season, it's quite difficult.
"Nothing is given, there's a lot of points to play for. But clearly the three teams are in a very advantageous position and everyone else will rely on how good we can be from now to see where that takes us.
"You need to be realistic. The top three have a great opportunity to win the title, the next four teams have a great opportunity to get into that fourth place and then you've got a real decisive battle to try to stay in the division."
In the last eight of the cup, Everton will travel to Arsenal, and there has been disquiet among Toffees fans over their ticket allocation of 5,186.
Martinez is sympathetic, and said: "We're disappointed because it's a major football event and we want to have as many fans as we can. We are a club that travel in huge numbers.
"It's something that's down to safety reasons and there's not much we can do. I understand the frustration from the fans and it's just making sure now that, for the ones who are fortunate enough to be with us, we make it an enjoyable afternoon."