The jury in New York took two days to convict Gupta on charges of securities fraud and conspiracy, the latest player to be found guilty in the biggest insider dealing investigation in US history.
Gupta, who was also managing partner of consulting firm McKinsey, faces more than 20 years in jail. He will remain free on bail until sentencing on October 18.
The 63-year-old was once one of the US's leading business figures. The prosecution accused Gupta of using his privileged status to supply insider tips to Rajaratnam, including information from Goldman Sachs.
In one incident Gupta called Rajaratnam a minute after taking part in a conference call with his Goldman Sachs colleagues at which the bank's boss, Lloyd Blankfein, announced billionaire investor Warren Buffett planned to invest $5bn in it.
Galleon, Rajaratnam's hedge fund, bought $43m of Goldman stock in the final three minutes of the trading day and made nearly $1m on the trade. Blankfein was called to testify in the case...