The key to successfully multitasking? "Get really good at saying no."
That's the message from Jared Leto, Academy Award-winning actor, rock star and successful tech investor.
"You have to be really good with your time. You have to be incredibly focused on what's important, what the priorities are," Leto told CNBC's "Squawk Box" in an interview Tuesday.
"In a band ... it's very similar to a start-up. You're a few people in a garage," he said, recalling the early days of "Thirty Seconds to Mars."
Leto learned to "play a lot of roles" with his band, not only as singer-songwriter but also as marketer and social media advocate.
"It put me on the path early on to be independent and entrepreneurial. And it lead me to the tech world," he said, adding tech investing was something he started to do quietly 10 years ago.
Leto has made more than 50 investments in early stage tech companies, including ride-hailing service Uber and home rental marketplace Airbnb. He serves as an advisor to several start-ups. He also founded a handful of small companies.
"I would say almost every investment I made I've been incredibly proactive, really aggressive," he said.
He was also an investor in smart home startup Nest, which Google purchased in 2014 for $3.2 billion and now resides under the Alphabet umbrella.
Even with such an impressive stable, there were companies that got away.
Leto recalled being too late to put money into the virtual reality startup Oculus, which sold to Facebook in 2014 for $2 billion. He also said he met with Instagram just days before Facebook announced its $1 billion acquisition of the photo-sharing site in 2012. "They were looking around and giggling. And I said, 'What's so funny?'"
They might not have laughed if they saw Leto's take on the Joker in the upcoming supervillain movie "Suicide Squad."
Leto said he perfected his Joker's maniacal laugh walking around the streets of New York City and Toronto. "I would kind of … see what laugh would would get under people's skin."
Known for immersing himself in his characters, Leto won the 2014 best supporting actor Oscar for playing a transgender AIDS patient in "Dallas Buyers Club." He also appeared in "American Psycho," "Fight Club" and "Girl Interrupted."
One of Leto's latest projects is a digital video series for AOL called, "Beyond the Horizon." Season 2 premiers this fall.
The show is billed as a look at the future of humanity with the world's most interesting visionaries. In Season 1, Leto interviewed NSA whistle-blower Edward Snowden, former Vice President Al Gore and American artist Jeff Koons. "Meeting Snowden was fascinating and interesting," Leto said.
"I saw a lot of your interviews," AOL Chairman and CEO Tim Armstrong told "Squawk Box," while on set with Leto. "Jeff Koons, if you are a fan of thinking about how human beings interact with technology and art, [is] maybe the best interview I've ever seen."
AOL was purchased by Verizon in June 2015 for about $4.4 billion.