Williams, a former world number one, secured her second title of the season and the 30th of her career in adding Miami trophy number five to the three straight she won from 2002 to 2004, plus her triumph in 2007. I feel like all I want to do is play tennis, be the best and win," Williams said.
"My whole life is dedicated to nothing but tennis. I've been working really hard."The 26-year-old American cruised through a 6-1 opening set in just 28 minutes as Jankovic, who has been battling a cold all week, made 11 unforced errors and struggled with her second serve.
However the Serb fought back to take the second set 7-5 before Williams, who failed to convert numerous match points, eventually won 6-3 in the third.
Williams, 26, has amassed a 47-5 win/loss record during her 10 appearances at the Miami hardcourt tournament, and also finished runner-up to sister Venus in 1999.
"I was definitely up and on my way to glory within an hour, but I started making a lot of mistakes, and Jelena obviously started playing better too," Williams said.
"Players who have nothing to lose are the most dangerous people in life on the court.
"I thought I had like 15 match points; I'm glad to know it wasn't. It was weird."