The 63-year-old star of "American Beauty" and drama series "House of Cards" is facing a four-week trial at Southwark Crown Court in south London.
Dozens of photographers and journalists gathered outside the court from 0530 GMT on Wednesday hoping to catch a glimpse of Spacey, who arrived by taxi with his legal team not long after 8.00am.
Walking past the cameras Spacey looked relaxed and gave a small wave, according to an AFP journalist.
Spacey has been on unconditional bail since first appearing in court in Britain last year.
The actor's stellar career has been halted by large numbers of allegations of sexual offences, although he has not been convicted of any crime.
Last year he appeared at London's Old Bailey court to plead not guilty to five offences against three men, including four counts of sexual assault.
They allegedly took place in 2005 and 2008 in London, and in 2013 in Gloucestershire, western England.
In November, prosecutors then announced seven additional charges involving another man, taking the total number of counts Spacey faces in the UK to 12.
The fresh counts, allegedly committed between 2001 and 2004, comprise three offences of indecent assault, three of sexual assault and one of causing a person to engage in sexual activity without consent.
Spacey, whose full name is Kevin Spacey Fowler, appeared at Southwark Crown Court in January to deny all the new charges.
He spoke only to confirm his identity and to enter the not guilty pleas.
None of the alleged victims can be identified under English law and reporting restrictions prevent further details being disclosed before trial.
Spacey enjoyed a highly successful acting career with roles such as a middle-aged father lusting after a teen in "American Beauty," a serial killer in "Se7en" and the villain in "Superman Returns".
He worked as artistic director at London's Old Vic Theatre between 2004 and 2015.
In 2017 he was one of the first stars caught up in the global #MeToo movement and was accused of sexual assault by multiple young men.
He was dropped from the final season of the political drama "House of Cards" and other projects.
Last year a New York court dismissed a $40 million sexual misconduct lawsuit brought against Spacey.
The complainant, actor Anthony Rapp, alleged the star had assaulted him when he was 14. He brought the civil case after being told it was too late to bring a criminal charge.
In 2019, charges of indecent and sexual assault were dropped against Spacey in Massachusetts.
In court appearances, Spacey has denied all allegations of sexual assault.