Barons survived a gritty late fightback by KK Zagreb to win the deciding third game of their quarter-final series 96-91 on Tuesday and progress to the EuroCup Final Four.
Armands Skele, the Latvia international guard, had 20 points and Dainius Adomaitis 19 to lead the Riga team to victory.
The triumph completed the Final Four with Barons' fellow Baltic side Tartu Rock of Estonia having advanced less than an hour before with a narrow triumph over Ural Great in their quarter-final decider.
Dexia Mons-Hainaut and Proteas EKA AEL had each booked their places in the Final Four last week with respective 2-0 sweeps of CSK-VVS Samara and Khimik.
Zagreb got 20 points apiece from Jakov Vladovic and Ante Tomic, but the young Croatians with national team aspirations weren't able to guide the team to victory.
A Skele jumper with 2:06 remaining gave the hosts a 93-85 lead but Zagreb's Nikola Garma replied with a three-ball for his first points of the game 15 seconds later to set up a thrilling finish.
With 1:17 to go, Tomic made the first of two free throws but missed the second to leave Zagreb behind 93-89. However, teammate Petar Babic grabbed the offensive rebound off the miss and went up for a lay-up to close the gap to just two points.
After Lithuania international Giedrus Gustas missed with a jump shot, Vladovic turned the ball back over to Barons and Skele went to the line and split a pair of free throws for a three-point lead with 19 seconds remaining.
Zagreb still had time but Vladovic turned the ball over again with nine seconds to go, this time with his pass being picked off by Demetrius Alexander.
Adomaitis killed the game off for the winners at the free throw line.
Zeljko Pavlicevic, coach KK Zagreb:
"I think it was a great game. Especially the first half was spectacular! Barons, for one or two balls, were better than us tonight. I was not surprised by their game, except for the three point shots. Barons go to the Final Four and I can only wish them good luck there."
Karlis Muiznieks, coach Barons:
"When it came to offense we managed to stick to our game plan, but it's been a long time since we last lost so many [easy] points. Because of our defensive errors our opponents wer able to keep it close till the end. Nevertheless we always believed in our victory. In the last minutes of the game my players did they job well."