The towering Swede, seeded third and winner in Adelaide last month, broke his opponent once in each set.
"I made a slow start today," said Johansson, who powered down 93 aces during the week. "I was not particularly nervous but I found it hard to read the way Ljubicic was playing.
"But I slightly changed my receiving position when he was serving and everything got much better. My game swiftly improved."
Eighth seed Ljubicic, playing in his second ATP Tour final this year, struggled to cope with the Swede's power.
"I never thought about breaking him," said the Croat. "But after we got to 5-5 in the first set, I had the feeling I had a chance to win.
"But he then lifted the level of his game and put much more pressure on me. I tried to force him to make mistakes but instead it was me who made them."
Victory provided sweet revenge for the Swede who twice lost to Ljubicic last year, at the Olympic Games and at the Madrid Open.
"I have improved dramatically over the last six months," added Johansson. "My serve is more solid and consistent, and I'm also much more patient on court."
The Swede, ranked 11th last week, should break into the world's top 10 with the third ATP title of his career.
"You have to set yourselves targets, like being in the top 100 and then in the top 10, if you want to become world number one," he said.
