The couple were reportedly salsa dancing at a restaurant when witnesses say Bieber's security asked everyone to put their phones away so as not to record the special moment.
Justin and Hailey first dated in 2016 before splitting and reuniting this year.
He also tagged Bieber's parents Jeremy Bieber and Pattie Mallette and wrote "Congrats" while sharing a Bible verse.
TMZ reports that Bieber, 24, proposed to Baldwin, 21, in the Bahamas on Saturday night.
The happy couple have been inseparable after they rekindled their romance just one month ago, after previously dating years before.
Forsberg strike clinches Sweden win over Switzerland
The referee initially pointed to the spot, only to overturn his original decision after consulting the VAR system. Sweden now await the victor of Colombia or England , with their quarter final to be played on Saturday.
The pair got engaged at a private affair in the Bahamas!
"In view of his 2.3 million Instagram followers today, he penned: "@justinbieber Proud is an understatement!
The source adds, "Hailey was smiling for ear to ear and said, 'Yes!' The two then embraced and the crowd erupted with cheers".
For his part, Bieber told GQ magazine in February 2016 that he wanted to be careful not to rush things with Baldwin in case she ended up being the one. "Excited for the next chapter!" he captioned a shot of his son watching the sunset over the ocean. Two days later, they made their new relationship Instagram official when Hailey appeared on his Instagram Story.
But Gomez, 25, didn't seem to have a care in the world as she was spotted living it up with her friends on a boat in NY on Sunday - hours after the engagement news broke. Heavy will continue to update as more information is known. In a second clip, Gomez cheers on a group of male friends, encouraging them to go for a dip in the Hudson River.