The couple took to Instagram to mark their milestone by publicly declaring their love for one another with matching posts.
Captioning the candid snap, he told his followers: “Happy anniversary to my best friend and wifey @haileybieber.. thanks for making me better in every way.”
Following on from his tribute, the 25-year-old model posted a slew of photos of the couple throughout their past four year, including one of them sharing a kiss on their wedding day, another of them looking cosy while driving in a convertible car.
The Rhode Beauty founder penned: “4 years married to you.
“The most beautiful human I’ve ever known… love of my life. Thank God for you.”
The couple got engaged in the Bahamas in July 2018 and secretly tied the knot at a New York courthouse in September of the same year.
They had a larger ceremony a year later in South Carolina, surrounded by friends and family including Kendall and Kylie Jenner.
The pair have been each other’s rocks in recent months as they both struggled with their health. In March, Hailey suffered a mini-stroke from a small blood clot on her brain.
In a YouTube video, she revealed that her body had managed to clear the clot by itself and later underwent surgery to close a hole in her heart following further investigation, making a full recovery.
Meanwhile, Bieber was forced to cancel some of his tour dates in June as he revealed he was battling Ramsay Hunt syndrome, which left him with facial paralysis on one side.
Ramsay Hunt syndrome (RHS) is due to viral reactivation and is one of 60 causes of facial palsy, or facial paralysis as it is known in the US.
Earlier this month, he announced that he would be taking another break from his Justice world tour to “make my health a priority” amid his ongoing recovery.
The Canadian singer said his recent shows in Europe had “taken a real toll on me” and he needs more time to “rest and get better”.
Posting on his Instagram story at the time, Bieber said he had given “everything I have” during a recent show in Brazil.
“After getting offstage the exhaustion overtook me and I realised I need to make my health the priority right now,” he said.
“So I’m going to take a break from touring right now. I’m going to be OK but I need to take time to rest and get better.
“Thank you for all your prayers and support throughout all this. I love you all passionately.”