Billionaire Shrien Dewani, 34, also denied paying three hitmen to kill his wife Anni on their honeymoon in November 2010 at Western Cape High Court.
Through defence lawyer Francois Van Zyl, Dewani said he has "had sexual interaction with both males and females".
"I consider myself to be bisexual," the court was told.
"My sexual interactions with males were mostly physical experiences or email chats with people I met online or in clubs, including prostitutes," Dewani's witness statement said.
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Anni's father, Vinod Hindocha, is in Cape Town with his wife and other family members from Sweden for the trial.
Dewani was extradited from the UK in April and is charged with conspiracy to commit kidnapping, robbery, murder, kidnapping, and defeating the ends of justice and has been receiving treatment at Valkenberg psychiatric hospital his arrival in South Africa.
Prosecutors argue that Dewani conspired with Cape Town residents Zola Tongo, Mziwamadoda Qwabe and Xolile Mngeni to kill his wife two weeks after their lavish wedding.
Taxi driver Tongo, Qwabe and Mngeni are already serving prison sentences in connection with the murder.
The trial is expected to last for around two months, presided over by judge Jeanette Traverso.