Both men had already been named in the RaboDirect PRO12 Dream Team for the season, and Nick Williams scooped the Players' Player of the Year award for his outstanding back row contribution to Ulster's march into the play-offs.
Luke Marshall picked up the Young Player of the Year title after not only breaking into the Ulster side, but also into the Ireland senior team.
After four seasons playing in the competition at Munster and Aironi, Williams headed to Belfast and revealed his full array of talents as he scored six tries in 16 appearances for Ulster in the RaboDirect PRO12.
At times unstoppable on the charge, he more than filled the gap left by the departure of Pedri Wannenburg at the end of last season.
The Kiwi back rower beat British & Irish Lions flanker Justin Tipuric and Glasgow Warriors' Fijian scrum half Niko Matawalu to the league's top gong.
He follows in the footsteps of Tommy Bowe (Ospreys), Ruan Piennar (Ulster) and Tim Visser (Edinburgh) in picking up the prestigious award.
Marshall had only started five games for Ulster in the RaboDirect PRO12 before this season, yet he grew into the centre role and not only played 11 times, but also won three caps in the RBS 6 Nations.
The 22-year-old struck up a great partnership with Darren Cave in the Ulster midfield and earned rave reviews throughout the campaign for his tough defence, good distribution and eye for a gap.
He beat Cardiff Blues out-half Rhys Patchell and Connacht full-back Robbie Henshaw to the title and follows in the footsteps of Tim Visser (Edinburgh), Toby Faletau (Newport Gwent Dragons) and Stuart Hogg (Glasgow Warriors) as the RaboDirect PRO12 Young Player of the Year.
It was a good night for Ulster, who host the Scarlets in the first of the two semi-finals at Ravenhill on Friday night, as they also scooped a £10,000 cheque to put towards youth development after winning the Specsavers Fair Play award for having the fewest yellow and red cards and citings over the 22 games - a mere six yellows.
They took over the mantle from play-off rivals Leinster, who had won it for the two previous seasons, who finished second with six yellows and one citing.
Another Ulsterman, winger Andrew Trimble, was acknowledged as the Try of the Year award winner for his memorable effort against Connacht at the Sportsground last month when he combined in brilliant fashion with Ruan Pienaar.
Former Scotland and Lions out-half Gregor Townsend won the Coach of the Year title from Ulster's Mark Anscombe and Benetton Treviso's Franco Smith after steering Glasgow Warriors into the play-offs.
His side put together a record number of wins during the campaign and finished in third place overall to secure an away trip to the RDS to face Leinster this coming weekend.
Leinster are the only team the Warriors failed to beat in the regular season, although they took a losing bonus point away with them from both matches.
Connacht's Michael Swift received the Chairman's award in recognition of his outstanding service to both his province and the tournament as a whole.
'Swifty' became the first player to break the league's 150-match barrier this season and completed his 164th appearance against Glasgow Warriors last Friday.
The 35-year-old London-born lock has played in every one of the 12 seasons of Celtic rugby and has signed for at least one more season with the westerners.
The Scarlets took over from Glasgow Warriors as winners of the Rhino Collision Kings title after a panel of experts assessed their efficiency at the breakdown and tackling, while Ian Madigan followed in the footsteps of his Leinster team-mate Jonathan Sexton and Munster's Ronan O'Gara in scooping the Rhino Golden Boot.
Madigan forced his way into the Dream Team for the first time and ended the regular season with 186 points from his 21 appearances, kicking 60 goals - 24 conversions and 36 penalties.
He only missed the target with nine attempts - three conversions and six penalties - and ended with an 87% success rate, including landing his last 21 kicks in a row.
Ospreys skipper Alun Wyn Jones, another player to make the Dream Team, took over from fellow Welshman Nigel Owens as the winner of the RaboDirect Straight Talking title.
2012/13 RaboDirect PRO12 Dream Team: Stuart Hogg (Glasgow Warriors); George North (Scarlets), Jonathan Davies (Scarlets), Luke Marshall (Ulster), Tim Visser (Edinburgh); Ian Madigan (Leinster), Niko Matawalu (Glasgow Warriors); Ryan Grant (Glasgow Warriors), Leonardo Ghiraldini (Benetton Treviso), Adam Jones (Ospreys), Alun Wyn Jones (Ospreys), Al Kellock (Glasgow Warriors), Alessandro Zanni (Benetton Treviso), Justin Tipuric (Ospreys), Nick Williams (Ulster).
2012/13 RABODIRECT PRO12 AWARD WINNERS:
PLAYERS' PLAYER OF THE SEASON - Nick Williams (Ulster)
YOUNG PLAYER OF THE SEASON - Luke Marshall (Ulster)
COACH OF THE SEASON - Gregor Townsend (Glasgow Warriors)
CHAIRMAN'S AWARD - Michael Swift (Connacht)
RHINO GOLDEN BOOT - Ian Madigan (Leinster)
RHINO COLLISION KINGS - Scarlets
SPECSAVERS FAIRPLAY AWARD - Ulster
RABODIRECT STRAIGHT TALKING AWARD - Alun Wyn Jones (Ospreys)
TRY OF THE SEASON - Andrew Trimble (Ulster v Connacht, April 2013)