Perth led the five-game grand final series 2-1 before Sydney Kings' coronavirus concerns forced the NBL to cancel the final two games on Tuesday.

The NBL referred to its rule book in handing down a decision, which ensured Gleeson won his fifth championship in seven seasons with the club.

Gleeson, who has only been coach of the year once, during his stint at Townsville Crocs, has now led the Wildcats to titles in 2014, '16, '17, '19 and '20.

Perth Wildcats have now won a competition-high 10 titles.

"It doesn't have the same feel, not being able to share it with the Red Army, having them there to help celebrate with us," Gleeson said.

"But I am so happy for these guys, it was a great season for us.

"It's a relief. So proud of the guys to be able to be rewarded for all the hard work they did.

"We made our points (to the league) with the three games that had been completed.

"I think the NBL made the right decision and we're happy with the result."

NBL commissioner Jeremy Loeliger said the league was governed by its by-laws.

"We feel that the rules set out in the NBL operations manual are clear in this regard," he said.

"In this instance, games four and five were cancelled by the league due to unforeseen circumstances pursuant to Rule 34 of the NBL operations manual.

"Consequently, the champions of the 2019-20 NBL season are the Perth Wildcats."

All three completed games of the grand final series went the way of the away team.

Perth stunned Sydney in game one - played in front of a bumper 11,000-plus crowd before the COVID19 restrictions forced fans out, winning 88-86.

The Kings levelled the series on the Wildcats' home floor in game two 97-83.

The Wildcats responded with a 111-96 victory at Qudos Bank Arena in game three before the series was cancelled.

League MVP Bryce Cotton was named player-of-the-series.

"Bryce's leadership this year has been first-class, it's always been team-first, all the way through," Gleeson said.

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