The 21-year-old American model and 23-year-old British singer looked very much together as they stepped out in New York days after their reported split.
Hadid was spotted holding Malik's hand and clinging to his arm as they left her apartment Friday. The pair, who were first linked in November, were rumored to have broken up earlier this month.
"Gigi and Zayn are back together. They spent part of this week together and spoke about some issues they had and decided they want to work it out with each other," a source told E! News.
Hadid had subtly denied breakup rumors by mentioning her "boyfriend" in an interview last week. She followed up Friday's outing by supporting Malik in a tweet Sunday after the singer canceled a show due to anxiety.
"I've seen the battles you go through and the way you fight to get to a place that allows you to get up there for your fans," the star wrote. "Your bravery in those times makes me proud, but your honesty last night proved what you're all about, being real."
"We are all here to support you and make each experience easier," she added. "Your talent and good heart will never lead you wrong. Love you and so proud of you always :) xG."
Malik was scheduled to perform at the Capital Summertime Ball in London. The singer released his debut solo album, Mind of Mine, in March after leaving One Direction in 2015.