The 6'6" Stormers lock, who weighs in at 120kg, was also a winner of the ABSA Under-21 competition with Western Province in 2010. It is anticipated that he will link up with Leinster upon the completion of his Super 15 commitments in time for the start of the PRO12 campaign.
Twenty-nine-year-old Goodman joins on a one-year deal with the option of a further year after recent spells with Nelson RFC where he was the club's player of the year for three consecutive years (between 2006-08). During this time he also featured prominently for Tasman Makos in the National Provincial Championship.
Though selected for the wider Crusaders panel in 2009, the 6'2" playmaker decided to take up the offer of a contract with Honda Heat Rugby in Japan before returning to Tasman Makos - whom he captained in the 2011 season - where he was the fourth highest points scorer in last year's ITM Cup (NPC).
Commenting on the deals, Leinster Coach Joe Schmidt said: "We are pleased to secure the signing of Quinn and Andrew who will bolster our second row and out-half/midfield options respectively.
"Quinn is a physically imposing forward with a burgeoning reputation in South Africa and he will add further competitiveness to the second row alongside Leo Cullen, Damian Browne, Devin Toner and Mark Flanagan as well as our other recent signing Tom Denton.
"Andrew is a quality player and has been a consistent place-kicker for a number of years.
"Both players are determined to make a positive impression over the forthcoming season and we are very pleased to have secured their services.
"We are also delighted that Luke has committed to the province for another year. Luke is an outstanding talent and he has played a major role in Leinster's recent success.''