Shani started investing in the 1980s. He founded Oshap Technologies in 1982. It was listed on the NASDAQ three years later, in 1985. By 1999, he sold it to SunGard for US$210 million. He was also a co-founder of Sapiens International Corporation and Tecnomatix, two companies listed on the NASDAQ which he later sold.
He founded Global Village Telecom, a Brazilian telecommunications company, in 1999. Upon selling it to Vivendi for US$4.5 billion in 2009, he made a profit of US$1.5 billion.
In May 2015, his net worth was estimated at US$3.0 billion.