Menendez made no comment to reporters as he and his wife walked into the US District Court for the Southern District of New York.
Last week, the Justice Department unsealed an indictment charging Menendez, his wife, and three other individuals with crimes including conspiracy to commit bribery, fraud, and extortion under color of official right.
Menendez allegedly exchanged his influence as a lawmaker to enrich himself and the other co-defendants, as well as to benefit the Egyptian government. The bribes allegedly included cash, gold bars and a luxury vehicle.
The senator defended his policy record on Egypt, pointing to his work on promoting human rights in the country, and said he withdrew thousands of dollars in cash from his own personal bank accounts as an emergency measure.
The allegations have prompted some fellow New Jersey politicians, including Governor Phil Murphy and Congresswoman Mikie Sherill, to call on Menendez to resign from his Senate seat. Menendez has agreed to temporarily step down as Senate Foreign Relations Committee chairman until the case is resolved.
Menendez said on Monday that he believes he will be cleared of bribery allegations and will continue to serve in Congress after the facts of the case against him emerge.