The cryptocurrency was trading at $37,176.44 at around 11:42 p.m.
On Wednesday, lawmakers in the Central American country passed a law that made bitcoin legal tender.
Among other things, it means prices can now be shown in bitcoin and tax contributions can be paid with the digital currency.
Bitcoin proponents, who have long seen the digital coin as a viable alternative to fiat currencies, welcomed El Salvador's moves.
The country has struck a partnership with digital wallet company Strike, to build the country's modern financial infrastructure using bitcoin technology.