A memorable week for Krajinovic continued as he saw off fellow Serbian Laslo Djere 6-4 6-2 in his semi-final.
No.6 seed Krajinovic defeated Stefanos Tsitsipas in the quarter-finals and ensured he followed up on that surprise victory with a dominant display against Djere on Sunday (AEST).
The victor committed only seven unforced errors in the match, while conceding just two break points in the contest.
No.2 seed Carreno Busta has not dropped a set all week and kept that run going with a 7-6 (7-2) 6-3 win over Federico Delbonis.
Carreno Busta needed just under two hours to see off a battling Delbonis, with neither player offering up a single break point in a first set that went the distance.
The Spaniard won five straight points to take the tie-break and continued that momentum into the second set when he broke Delbonis twice.
Neither Carreno Busta nor Krajinovic have ever won a tournament at ATP 500 level or above.
Carreno Busta has five career titles, but all of those are at ATP 250 level, losing to Dominic Thiem in his only showpiece appearance at this level at the Rio Open back in 2017.
Krajinovic, meanwhile, has lost all three of the career finals he has reached.
"I enjoy playing here, I feel comfortable here," Carreno Busta said. "It is my most important match this year on Sunday [Monday AEST] – I need to be really focused until the end.
"[Delbonis] is a really tough player and my level was very good. I probably played better in the second set, but I continued fighting all the time."
At the Nordea Open in Bastad, Sweden, No.1 seed Casper Ruud was comfortable as he defeated Roberto Carballes Baena 6-1 6-4 to earn a place in the final.
Ruud needed just 79 minutes to do the job, breaking Carballes Baena on five occasions.
He has only played two matches – both comfortable wins – to reach the final after a walkover against Henri Laaksonen in the quarter-finals.
Rising star Ruud will bid for his second ATP title of the year and the third of his career against Federico Coria on Monday (AEST).
Coria also had a comfortable last-four tie, seeing off Germany's Yannick Hanfmann 6-2 6 -1, with the win meaning the 29-year-old reached his maiden career tour final.
"I am very happy – it is my first final," world No.77 Coria, who beat No.2 seed Cristian Garin in the last eight, said.
"I played the best tennis of my life in this match. It is amazing here in Bastad, it is beautiful."