Bitcoin slipped 5% after Musk fired off tweets that appeared to lament a breakup with the cryptocurrency.
The price fell after he posted "#Bitcoin", a broken-heart emoji and a picture of a couple discussing a breakup.
Musk followed up by replying "nice" to an illustration of rival currency dogecoin posted by crypto exchange Coinbase.
It was unclear what, if anything, any of the tweets meant.
Musk has previously said Tesla would not sell its bitcoin, but his tweets were enough to unsettle markets still fragile following May's crash.
Some on the digital currency scene accused Musk of "trolling the community".
Despite Friday's fall, bitcoin has still climbed nearly 6% over the past few days and is on course for its best week in about a month.
Musk has been a major promoter of cryptocurrencies.
But has turned critical of bitcoin since suspending Tesla plans to take it in payment for cars.
Bitcoin and several other cryptocurrencies are still recovering from a crash last month in the wake of that decision.
As well as news of renewed regulatory scrutiny in China.