Andreescu broke Kerber three times in the third set, rallying from a 3-2 deficit to take four of the final five games.
She dropped her racket near the baseline and fell on her back, her legs in the air as she covered her face in disbelief.
After getting up and exchanging kisses with Kerber, the teen bent down and kissed the sunbaked hard court and dropped to her back again, her arms and legs splayed, before grabbing her head.
“This moment has become a reality so it’s really, really crazy,” Andreescu told the crowd before speaking in Romanian.
Born in Canada, she later moved to Romania with her parents and first started playing tennis.
German Kerber was the last of five seeded players – and fourth top 20 player – that Andreescu knocked off in her seven matches in the desert.
Kerber remains without a title since she won Wimbledon last year.
Andreescu is projected to rise 36 spots to No.24 in the WTA Tour rankings on Monday after she started the year at 152nd.
Leading 2-1 in the third, Andreescu took a medical timeout and had a trainer massage her right shoulder and arm.
Kerber won the next two games, breaking Andreescu to go up 3-2.
Andreescu won the next three games as she ripped powerful forehands and won nine-straight points during one stretch.
She had three match points on her serve at 5-3 but couldn’t close out the match but broke Kerber’s serve one final time to secure her maiden tour title.