The pair have been together for just over four years, after they celebrated their fourth anniversary in February this year.
"4 years loving you," Natalie shared to her Instagram at the time.
The couple often share sweet tributes to one another to their respective Instagram profiles, with Harley even hinting to the proposal a day before it happened.
"Tough weekend to top.. More to come," he captioned a photo on Sunday.
News of their engagement was met with love and excitement, with Harley's Home and Away co-stars taking to the comments to congratulate the happy couple.
"Harley!!! Congratulations beautiful man! I look forward to meeting your gorgeous FIANCÉ one day!" former star Penny McNamee wrote.
"Congrats guyssss," Sophie Dillman said, with Ethan Browne adding: "Yeyah! Congratulations brother!"
Georgie Parker also said: "Congratulations you two," followed by Rob Kipa-Williams who wrote: "My man.. Congratulations to you both.. Much love brother.."
It comes after Harley and Natalie took a romantic getaway this weekend, with the model sharing clips of their accommodation - moments before the proposal.
Natalie also shared the moments after she said yes, where she penned: "Didn't think I could love him more. @harleympb, my forever."
The couple celebrated their engagement with Champagne, flowers and phone calls home to their family to share the good news.
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