Fifty-four of the 100 senators signed the letter, which accused Turkish President Recep Tayyip Erdogan of marginalizing domestic opposition, silencing critical media, jailing journalists and purging independent judges.
"We urge you to emphasize to President Erdogan and his administration that they should immediately end their crackdown on dissent at home and abroad, release political prisoners and prisoners of conscience, and reverse their authoritarian course," the letter said.
NATO ally Turkey has said recently that it wants to improve relations with the United States under Biden, after Washington last year imposed sanctions over Turkey's purchase of a Russian air defense system.
Biden is expected to be tougher on Ankara over its record on human rights. Since a failed coup in 2016, Erdogan's government has detained nearly 300,000 people and has suspended or dismissed more than 150,000 civil servants. Hundreds of media outlets have been shut and dozens of opposition lawmakers have been jailed.