Altman is considered by many in Silicon Valley as one of the savviest tech investors around, thanks to his early stakes in Airbnb, Dropbox, Pinterest, Reddit and Zenefits.
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Tuesday on CNBC's "Power Lunch" Altman was asked whether he thought a valuation bubble existed in the tech world.
"There are a lot of people who try and speculate where in the cycle we are," said Altman. "At Y Combinator, we try to think instead of the next decade, and the decade after that. So if you invest on that sort of time frame…about how awesome the world is going to be in twenty years, than everything here just looks like noise."
Altman remains convinced high valuations for many of today's startups are "reasonable" and "still connected to reality," even for those with multi-billion valuations, or so-called "unicorns." But he is not blind to the dangers lurking within a zero-rate environment.
"We get worried if companies don't have profitability within their grasp or are too dependent on outside capital."
With that in mind, Altman insisted it all comes back to correct valuations from the get-go.
"We invest in very, very early stage companies. Two or three people and an idea, with a $120,000 investment in return for a seven percent stake. No matter what the cycle is, up or down, our valuation never changes."
These days, Altman is funding more and more hardware startups and companies focused on building things like nuclear reactors and rockets,
As for the leadership in Silicon Valley, Altman addressed the growing trend of dual CEO roles, on the heels of Jack Dorsey being named Twitter's CEO while simultaneously keeping his corner office at Square.
CNBC's Krista Braun contributed to this article