Kokkinakis was on course to secure victory in Friday's semi-final at Memorial Drive after opening up a 6-2 lead in the third-set breaker.

But nerves got the better of him when it mattered most, with the 25-year-old squandering all four of his match points - three of which were errors off his racquet.

He then had to save two match points himself, before wasting two more of his own match points.

But Kokkinakis finally sealed the win on his seventh match point when Cilic hit the ball into the net.

Kokkinakis roared with delight and soaked up the crowd atmosphere at his hometown event as the significance of his 6-2 3-6 7-6 (12-10) triumph began to sink in.

The rejuvenated world No.145 will take on Frenchman Arthur Rinderknech in Saturday's final.

It will be Kokkinakis' first appearance in an ATP final since losing the decider of the Los Cabos to Sam Querrey in August, 2017.

"I played a great breaker up until 6-2 and then I tightened up like nothing else," Kokkinakis said of his dramatic win over Cilic.

"He got match point up and I was like, 's**t, I'm in some strife here'.

"When all those match points went I'm like, 'oh god, I can't wait to hear about this on Twitter and in the headlines that I'm a choke artist and all this'."

The big-serving Adelaide player's potential has always been clear, most notably when he beat 20-time grand slam winner Roger Federer in Miami in 2018.

But his hopes of becoming the top 10 player that many tipped him to be have been thwarted by numerous injuries, including shoulder, pectoral, groin, knee, and elbow issues.

Kokkinakis still has time on his side, and a triumph in the second of the Adelaide International warm-up tournaments before the Australian Open, could prove to be a launching pad to something special.

"To come out and play good matches and back it up was the biggest thing," Kokkinakis said.

"That was the question mark with me. People knew I could play the odd good match, but to do it consistently and to back it up, it's great.

"It's set me up for a real good position in the year. I couldn't be prouder of how I've started," added Kokkinakis, who also reached the semi-final of last week's first event at Memorial Drive.

Rinderknech swept into his first ATP final with a crushing win over countryman Corentin Moutet.

The rangy world no.58 Rinderknech won 90 per cent of points on his first serve in a dominant display to wrap up the victory 6-1 6-3 in 76 minutes.

"It's a great achievement," 26-year-old Rinderknech said.

"I'm really happy to be in the final - it's a new step again.

"I made the semi-final in Kitzbuhel last summer and now the final here for my first tournament of the year."

Australian Associated Press