In the second set, both players rode their serves early, with Osaka winning love games in the third and fifth games before Pliskova returned the favor in the sixth to tie the scores 3-3.
The newly-crowned US Open champion, who was bidding to become the first Japanese victor of the event since 1995, succumbed 6-4 6-4 in a battle of two big servers.More news: Zverev seals Laver Cup win for Europe
In the second round, Osaka, World No. 7, was due to take on China's Shuai Zhang, who defeated Samantha Stosur of Australia 6-2, 6-2.
"I was pretty nervous because I really wanted to get to the final", said 2016 runner-up Osaka, who fired down nine aces in a dominant display.
The Japanese, who beat Pliskova en route to the Indian Wells title this spring, appeared the more tired despite her quicker passage this week.
"The chances of me playing in the next tournament are very low", she added, only to pull out hours later. "The only thing that I could do is play as well as I can and hope for the best".More news: Paul Pogba wants return to Italian club Juventus
Osaka hit a series of unforced errors and showed none of the poise and power that secured her a first Grand Slam title.
Osaka earned a 6-2, 6-3 victory over the Czech in the quarterfinals of the BNP Paribas Open in March, en route to winning her first career title.
Prior to the final, Pliskova had spent 419 minutes on court, more than any other player and nearly twice as long as Osaka, but the Japanese player soon wilted and was unable to match the brilliance that secured her a first Grand Slam title. Osaka, bidding to become the first home champion here since Date in 1995, looked anxious throughout the contest and allowed Pliskova to win easily in just over an hour.
"It was important for me to play two sets and not go three sets - also for recovery for the next tournament - and I needed a match like this", Pliskova, fourth seed, said after the win. "She was missing quite a lot today so it was working, so I didn't change anything". That's normal in semifinals - there's no easy opponents."I think Donna was playing well and she's beaten a lot of tough players this tournament".More news: EPL: Cech speaks on 'rivalry' with Arsenal goalkeeper, Bernd Leno