The 22-year-old DR Congo international, nicknamed ‘The Wizard’, is the Whites’ eighth new arrival of the summer.
He told the club’s official website: “I am very happy, it happened very fast. In two or three days everything was arranged, it was just crazy.
“I knew Leeds were a big club. I looked a few things up and I heard from other people. This is a new adventure for me.”
Botaka, who was a regular for Excelsior, is currently on international duty with his country.