Manu Sharma, 31, was convicted for shooting Jessica Lall after she refused to serve him a drink at an upscale New Delhi bar because it was closing time.
Lall, who was a model and a celebrity, was serving drinks for one evening at a party at the bar.
The case was seen as a test of the Indian judiciary's willingness to take on powerful people accused of criminal offenses.
"There's a certain amount of closure now ... for all these seven-and-a-half years we've all been waiting and it's finally done," the victim's sister Sabrina Lall told reporters outside the courtroom.
The trial made headlines after a lower court acquitted Sharma earlier this year. Dozens of people witnessed the killing, but most later recanted their testimonies as the case moved through the courts.
The earlier acquittal drew sharp criticism from New Delhi's citizens, who held street protests for several days, forcing authorities to reopen the investigation.
Sharma is the son of Venod Sharma, an influential politician and former governing Congress party minister in northern Haryana state, with business interests in sugar mills, the AP says.
The High Court's guilty verdict came on Monday and it also found Sharma's friends, Vikas Yadav and Amardeep Singh Gill, guilty of destroying evidence and helping Sharma escape.
Cases can take decades to get through India's courts, with bribes often being openly demanded. The powerful seldom face prosecution.
In recent months, however, the courts have convicted several powerful people accused of crimes, including a Cabinet minister who was sentenced earlier this month to life imprisonment.