Neither celebrity admitted to or denied the charges in their settlements.
Floyd and Khaled were named in a lawsuit by jilted investors, who claimed they were bilked out of the money by a company Centra, which sold the so-called "CTR" token.
Mr Khaled was paid $50,000 by the same company, the SEC said.
In a statement Thursday, SEC Enforcement Division co-director Stephanie Avakian said that "with no disclosure about the payments, Mayweather and Khaled's ICO promotions may have appeared to be unbiased, rather than paid endorsements".
The promotions followed a 2017 report warning that coins sold as ICOs may be classed as securities and that anyone selling or promoting them should comply with federal securities laws that mandate anyone promoting a sale disclose their financial relationship to the company. Mayweather also didn't disclose promotional payments from three ICO issuers, including Centra Tech, which gave him $100,000, the commission added.
Another Mayweather post promoting a different cryptocurrency said "You can call me Floyd Crypto Mayweather from now on". It seems that neither Mayweather or Khaled got that message.
Crypto Ruling: Floyd Mayweather, DJ Khaled Sucker Punched By SEC
According to TMZ, Floyd Mayweather and DJ Khaled have been named in a lawsuit over their roles in a cryptocurrency scam.
In April 2018, the SEC filed a civil action against Centra's founders, alleging that the ICO was fraudulent.
The US attorney's office for the southern district of NY has filed parallel criminal charges against the pair.
Khaled was also warned separately that he was not properly disclosing other instances in which he was paid to promote products on social media, including in posts where he bragged about his love for Cîroc vodka.
"Investors should be skeptical of investment advice posted to social media platforms, and should not make decisions based on celebrity endorsements", said Peikin.
Mr Mayweather will repay the $300,000 he received, as well as a $300,000 fine and interest. This is a Game changer here.
The boxer has settled with the SEC and, as part of his punishment, will be banned from promoting any securities for three years.