The Hollywood star, 62, was ushered into Westminster Magistrates' Court on Thursday morning amid a media scrum after he got out of a silver Mercedes.
Spacey, wearing a pale blue suit, dark spotted tie and white shirt, smiled as he entered the building.
He faces four counts of sexual assault and one of causing a person to engage in penetrative sexual activity without consent.
The allegations relate to three men, now in their 30s and 40s, in London and Gloucestershire between 2005 and 2013, including while Spacey was artistic director of The Old Vic theatre in the capital.
The Crown Prosecution Service (CPS) authorised charges against him last month, but American Spacey could only be formally charged after travelling to the UK earlier this week.
Spacey, a two-time Oscar winner known for American Beauty, The Usual Suspects and House Of Cards, previously said that he would travel to the United Kingdom to face the charges, which he is expected to deny.
In a statement released to Good Morning America after the CPS' announcement, he said: "While I am disappointed with their decision to move forward, I will voluntarily appear in the UK as soon as can be arranged and defend myself against these charges, which I am confident will prove my innocence."
The most serious charge of causing a man to engage in penetrative sexual activity without consent is an indictable-only offence, meaning it can only be tried in the Crown Court.
Spacey, whose address in court documents is given as an apartment in Waterloo, was artistic director at The Old Vic between 2004 and 2015.
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