Brian Nichols is the co-founder of Angel Squad, a community where you’ll learn how to angel invest and get a chance to invest as little as $1k into Hustle Fund's top performing early-stage startups.

Sam Altman runs OpenAI, but that's only part of the story. Behind the scenes, he's built one of Silicon Valley's most successful investment portfolios. Studying Sam Altman investments reveals a disciplined approach to backing transformative technologies years before they become obvious.

The Scale: 400+ Companies, $2.8B

Using CB Insights data, Altman's investment portfolio includes stakes in over 400 companies since 2019.

Altman has investments through Altman Capital, Apollo Projects (founded with his brothers), and Hydrazine Capital (co-founded with his brother Jack in 2012).

This isn't spray-and-pray investing. It's a systematic approach to building a diversified portfolio across multiple investment vehicles.

The Mega Bets That Define His Strategy

Most angels write $25K checks. Altman writes nine-figure checks into his highest conviction ideas.

Helion Energy: In November 2021, Altman contributed $375M to Helion's $500M Series E raise, his largest personal investment to date. In May 2023, OpenAI-backer Microsoft signed an agreement to buy electricity from Helion later this decade.

Retro Biosciences: Altman invested a total of $180M in the company, which aims to extend life spans via cellular reprogramming.

These two investments accounted for "all my liquid net worth," Altman told MIT Technology Review.

Let that sink in. The CEO of OpenAI, with access to hundreds of investment opportunities, put essentially all his personal wealth into nuclear fusion and anti-aging research.

The Y Combinator Portfolio

During Altman's time leading Y Combinator from 2014 to 2019, he helped shape investments in some of the most successful companies of the decade.

Through Y Combinator, Altman helped lead investments in Cruise, Instacart and Reddit.

But the really interesting investments are the ones he made personally:

Airbnb: Altman is good friends with Airbnb CEO Brian Chesky. Altman invested $100,000 in Airbnb in 2008 when the company was in its short-term rental infancy.

Reddit: Altman previously served on Reddit's board and was even its CEO for eight days. He said in 2014 that he had been a daily Reddit user for nine years and got to know Reddit's founders at Y Combinator.

Asana: Altman was the lead investor in Asana's $50 million Series C round in March 2016 and participated in the follow-up $75 million round in January 2018. At the time, Altman argued that Asana solved communication problems in business and predicted it could massively increase productivity for hundreds of millions of people.

The Investment Thesis: Fundamental Technology Shifts

Analyzing Sam Altman investments reveals clear patterns:

He invests in companies building fundamental infrastructure

From Stripe (payments) to Helion (energy) to OpenAI (AI), Altman gravitates toward companies creating new technological foundations that other companies will depend on.

He takes extremely long-term views

Altman is known for taking a long-term view of his investments, understanding that some bets take decades to pay off.

He backs founders solving existential problems

Nuclear fusion solves energy scarcity. Anti-aging research addresses mortality. AI tackles intelligence augmentation. These aren't incremental improvements; they're moonshots.

He diversifies across multiple sectors

Altman has a diverse portfolio spanning biotech, AI, fintech, and more. This diversification helps spread risk.

How Altman Actually Adds Value

Altman doesn't just invest money; he often takes an active role in advising and mentoring the startups he supports.

His experience running Y Combinator gave him pattern recognition across thousands of companies. He understands what works and what doesn't at different stages of company building.

More importantly, his network is unmatched. An introduction from Sam Altman opens doors that remain closed to other investors.

Recent Investments: Following the Frontier

In 2024, Apollo Projects took part in the $195 million round for KoBold Metals. The company uses artificial intelligence to mine for valuable metals such as cobalt, copper, nickel and lithium used in electric vehicle batteries.

This investment ties together several Altman themes: applying AI to hard problems, building clean energy infrastructure, and backing founders tackling planetary-scale challenges.

Early Success Stories

One of Altman's early investments was Codecademy, which he backed in 2011. The company was acquired for $525M by SkillSoft in December 2021.

Other early investments that went on to exit include Instacart (the company IPO'd in September 2023) and Cruise (acquired by General Motors in 2016).

Key Lessons For Early-Stage Investors

Build a diversified portfolio over many years

Aim for a portfolio of at least 10 startups, with each investment representing no more than 10% of your overall portfolio.

Do your due diligence religiously

Research potential investments thoroughly, not only looking at financials and market opportunity, but also talking to customers, competitors, and other stakeholders.

Take extremely long-term views

Don't expect immediate returns. The best investments often take 7-10 years or longer to mature. Be prepared to hold through multiple market cycles.

Focus on fundamental technology shifts

Look for companies building infrastructure that other companies will depend on. These platform businesses tend to have higher multiples and more defensible moats.

Only invest what you can afford to lose

Startups are speculative. You shouldn't invest anything you're not comfortable kissing goodbye. Treat it as casino money.

Get actively involved

The most valuable investors provide strategic advice, make introductions, and help companies navigate difficult decisions. Don't be a passive check writer.

The Bottom Line

Sam Altman investments represent a masterclass in building a diversified, high-conviction portfolio across transformative technologies. His willingness to invest hundreds of millions in nuclear fusion and anti-aging research shows genuine conviction in backing companies solving existential challenges.

Combined with his systematic approach through Y Combinator and his various investment vehicles, Altman has built one of the most successful investment track records in Silicon Valley.

Want to develop the pattern recognition and disciplined approach that successful investors like Altman use? Angel Squad is where operators-turned-investors share tactical lessons on building portfolios, evaluating early-stage deals, and accessing top-performing startups with investments starting at just $1K.