Bitcoin, the world's biggest digital currency, rose more than 4% after Musk's tweet and was last trading at $56,429.
The round was led by Coatue, Ribbit, and Stripes with strategic investment from The Bank of New York Mellon and SVB Capital.
In an interview with CNBC, Twitter's CFO said the social media had considered how it might pay vendors or employees using bitcoin.
Tesla said in a filing the decision was part of its broad investment policy as a company and was aimed at diversifying and maximizing its returns on cash.
The bitcoin farms consume about 300 megawatts of electricity per hour, about the same as a town of at least 100,000 residents.
Musk wrote simply "#bitcoin" in his biography on the social media site.