"And if it doesn't work, he's gonna sue death!" Musk tweeted.
Musk, who has previously taken jabs at his billionaire space race rival on social media, was replying to the Twitter account Say Cheese, which posted that Bezos had invested in the startup.
According to MIT Tech Review, the Amazon founder is reportedly one of a group of investors backing Altos Labs, which is working on biological reprogramming technology to essentially prolong human life.
The startup, according to MIT Tech Review, has plans to create institutes in California, Cambridge and Japan. It is also seeking university scientists and offering them salaries as high as $1 million so they can dedicate their research on how to reverse the process of aging cells.
Musk's latest comment comes roughly a week after he took a jab at how Bezos, the founder of Amazon and space exploration company Blue Origin, spends his time after stepping down as chief executive of the e-commerce giant.
"Filing legal actions against SpaceX is *actually* his full-time job," Musk tweeted.
Musk was referring to Amazon's attempt to throw a wrench in SpaceX's second-generation Starlink satellite program.
Bezos' investment office, Bezos Expeditions, did not respond to FOX Business' request for comment.
FOX Business' Breck Dumas contributed to this report