Ricciardi, who served as GM of the Blue Jays from 2001-09, was an analyst with ESPN last season.
"I'm very pleased to announce J.P. Ricciardi agreed to join the New York Mets," Alderson said in an introductory conference call with Ricciardi. "He's going to be valuable in a lot of things we do, but particularly in player-related activities such as amateur and pro scouting, player development and trades."
In his new role, Ricciardi -- who worked for the Oakland Athletics for 16 years (1986-2001), including 12 years (1986-1997) when Alderson was the club's GM -- will assist Alderson in all aspects.
"I'm very excited to be with the Mets," Ricciardi said. "I want to thank Sandy for thinking of me and giving me an opportunity to come over here. As most of you know, I played in the Mets system, so it's a bit of a homecoming for me. I'm really confident we can get the Mets going in the right direction and help them become a playoff club."
Ricciardi, 51, played two seasons in the Mets' Minor League system in 1980 and '81 after signing as a non-drafted free agent. He became a scout in the A's organization in 1986 and considers his biggest asset to be his experience in player development.
"I think having a background in player development and scouting has always been my strength," he said. "I also think having been a general manager for eight years and seeing the pace of what goes on and what it's like to sit in that chair is helpful."
Alderson praised Ricciardi, who turned down a similar offer from the Red Sox, for his work with the A's and Blue Jays.
"I worked with J.P. a long time in Oakland, of course, but his career goes way beyond that," Alderson said. "He had even greater achievements after I left Oakland and in Toronto, where he was very successful in developing young talent."
Ricciardi's hire might not be the last front-office addition for the Mets, as Alderson has hinted that the club is looking to bolster the staff. Former Dodgers GM Paul DePodesta has been rumored to be a candidate to join the organization.
"We're still talking with other possible additions," Alderson said. "We're still looking and possibly talking, so we'll see how that goes the next few days or weeks."
As for the managerial search, Alderson said that all internal candidates have been notified and that interviews will begin this week. He did not name the internal candidates, however, and said the club has not officially contacted any external candidates, as they are still compiling a list, with interviews to begin sometime next week.
Alderson did describe what the organization is seeking.
"I think we all agree on the relevant qualities, but every individual is different," he said. "What we're looking for is a package. So I don't think we can prejudge anyone before we have a conversation. It's not just what they say, it's their enthusiasm and their desire."
Rhett Bollinger is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.