While he's continued trading even as "Wall Street: Money Never Sleeps" opens in theaters on Friday, he admits the business has a serious impact on his world outlook.
"That's the thing it does for you, it changes you," he tells PopcornBiz, admitting it can often lead to a thought-process that's "cynical and nihilistic"
For example, he viewed he news of the massive Russian fires last month more as a business opportunity than through his usual lens of seeing humans in peril.
"A normal person sees a huge fit in Russia and they show some empathy for these people," LaBeouf says. "What are they going to do? Who is going to help?"
"My mind doesn't work like that anymore," he admits. "I hear there's a fire in Russia and I'm buying wheat."
"It's a dark way to think."
While the sometimes intense practice started as training for the film, LaBeouf has continued long after it wrapped and admits his trading portfolio was having "a good September" after a poor August.
The practice also allowed him to humanize the character he was going to play by showing that people on Wall Street are just people as well.
"Before I had any info it was very easy to vilify Wall Street and capitalism," says LaBeouf. "It was so black and white. These people are villains. But you cannot just blame it on these people."
Americans are also to blame for their out-of-control spending habits which led to the economic problems which plague the country.
"When you have a bunch of heroin addicts at a party who are trying to clean up, you don't throw a dime bag on the floor," says LaBeouf. "Americans, we're a bunch of heroin addicts. And Wall Street threw the dime bag."
"Who is wrong there? They are both wrong. It's the American way of thinking that needs to change," he adds.
By the way, there's little chance that LaBeouf will quit the acting day-job to take trading on full-time.
"Money doesn't give me passion like what I do," the star says. "I don't thrive off money the same way."