World No.2 Djokovic was the defending champion in the men's singles category. He also won the title in Miami six times.
"I have some very disappointing news to share with you regarding the Miami Open tournament. My doctor has strongly advised against play because my elbow injury, that I keep carrying on for months, got worse in the past week," Djokovic posted on Facebook on Sunday.
"I will do everything in my power to recover and do all the necessary therapy to be able to return on court as soon as possible," he added.
"Sadly, I won't be able to defend my title in Miami this week. Believe me, it is as shocking to me, as it is to you.
"I had incredible run in Miami, I won there my first masters tournament and started my campaign towards the top of the world rankings."
Murray said in a release: "Sadly due to a right elbow injury, I won't be playing in Miami. Apologies to the fans, it's one of my favourite tournaments. The focus now is on getting ready for the clay season."