The 24-year-old Chopra, who had pulled out of the Birmingham Commonwealth Games due to a "minor" groin injury he had suffered while winning a silver during the World Championships last month, hurled the spear to 89.08m in his first attempt to seal the win in style.
Chopra rested and rehabilitated for a month but it looked like the injury had not happened at all as he continued his vintage form.
The 89.08m throw was his third career-best effort. His second throw measured 85.18m before passing on his third attempt. His fourth throw was a foul while he again passed his fifth attempt before coming up with 80.04m in the sixth and last round.
Only the top three after the fifth round get the sixth throw. The youngster from Khandra village near Panipat in Haryana became the first Indian to win a Diamond League crown.