It will add two months onto her current arrest, keeping her there until at least May.
Griner was detained at a Russian airport after customs reportedly found cannabis oil in her luggage.
A Moscow court announced on Thursday that Griner will remain in custody.
“The court granted the request of the investigation and extended the period of detention of the US citizen Griner until May 19,” Tass reported the court as saying.
The US State Department said that US diplomats are “closely engaged on this case and in frequent contact with Brittney Griner’s legal team.”
Talking to the BBC, their spokesperson added: “We insist the Russian government provide consular access to all US detainees in Russia, including those in pre-trial detention, as Brittney Griner is.”
“Russia must abide by its legal obligations and allow us to provide consular services for US citizens detained in Russia.”