Andreescu, 18, reached the fourth round of the Miami Open, winning 6-4, 4-6, 6-1 in a match that ended early Sunday.
Andreescu took a medical timeout after seven games to receive treatment on her right arm.
"Biggest drama queen ever," Kerber told Andreescu while offering only a brusque handshake following the match.
The Canadian defeated Kerber in the Indian Wells final for her first career title.
Kerber was seeded eighth at Miami, and Andreescu is unseeded. The win was Andreescu's 12th in 2019 against a top-50 player. She had only one before this year.
Also, Venus Williams reached the fourth round of the tournament for the 16th time with a 6-3, 6-1 win over No. 14 Daria Kasatkina. Williams lost serve four times but won every return game, going 8-for-8.
"I've never had a match like that before in my life,'' she said. "There's always a time for a first. I'm returning really well.''
Williams won the title in 1998, 1999 and 2001. She's unseeded at Miami for the first time since 2012 but seems to be enjoying herself, smiling often, including when Kasatkina hit a shot between her legs.
"I never smile on the court, and this week I've smiled a lot,'' Williams said. "There's a lot to smile for. That's all I can say.''
"I was running like crazy for three hours,'' Halep said. "If I keep doing this, I think I have a chance to be back No. 1.''
A loss Saturday by top-ranked Naomi Osaka opened the door for Halep to reclaim the top ranking if she reaches the final.
No. 25 Danielle Collins lost to Wang Yafan 7-5, 6-1.
The Associated Press contributed to this report.