The title race appeared set to head to the season finale in Japan next month, an event which is among the seven points-scoring rounds selected by the Toksport Skoda Fabia driver.
Mikkelsen finished this weekend's 18-stage asphalt contest in 13th overall after his hopes of challenging for the class victory evaporated following an off in treacherous wet conditions on Friday.
The off-track excursion cost the three-time WRC rally winner 10 minutes, dropping outside of the top 10.
His closest title rival Yohan Rossel had already retired after hitting a tree on stage three, which left fellow Toksport driver Gus Greensmith as the only driver that could force the championship battle into Japan, although this is an event not part of the Briton's programme.
Greensmith finished the rally in fourth despite losing time to a puncture on Friday. But any hopes of forcing Mikkelsen to score points in Japan came to an end on the Power Stage.
Greensmith failed to register any points, while Mikkelsen claimed the full bonus points which left the pair on 111 points apiece.
However, with Mikkelsen claiming three wins (Sardinia, Estonia and Greece) compared to Greensmith's Mexico and Portugal maximums, the title went to Mikkelsen.
"Our weekend was not fun as we were just waiting for the Power Stage but we did that perfectly so it is a very nice feeling," said Mikkelsen.
"We knew we had nothing to lose. It was win it or bin it for us. I was happy when we saw the finish as we were pushing like crazy."
Mikkelsen's second WRC2 title to add to the one he scored in 2021 with Skoda is even more impressive considering his campaign only began in Portugal in May, and the fact he wasn't planning to run a full programme. The triumph was also achieved without dropped scores.
"It has been really tough because I knew if we made one mistake we would probably not get to do any more rallies, but we got rallies because we delivered," he added.
"There was high pressure all season not to do any mistakes, drive clever and do what was expected."
Mikkelsen said he doesn't have a deal in place for next season but would like to remain with Skoda in Rally2 if there is an opportunity.
"I've been very honest with Skoda that our history goes a long way back until 2011," he said. "In 2012 when I lost my chance with Volkswagen they stepped in and helped my career. When Hyundai went out, they stepped in and then also this year.
"As long as I have some kind of offer or deal with them, I will never drive for an opposition of them. First priority in Rally2 will always be Skoda."
