Walker died in a car crash on November 30, 2013.
Gibson shared a photograph of the two together on Instagram, confessing that he continues to struggle with Walker’s death, reports people.com.
“It’s still not easy… Two years ago today, we lost our brother. Today I’m just going to lay low and process. Clarity through prayers and perspective is what I always seek and pray for (sic),” Gibson captioned the image.
“With a heavy heart I post this… Please continue to pray for the Walker family and his real friends who were with him every single day. They’re some of the best and strongest people I know. I know you’re in heaven smiling and rooting for us all,” he added.
Diesel also took to social media to remember his “brother.”
“No matter where you are in the universe… You will always be my brother,” Diesel wrote on Facebook.
The actor also posted a photograph of the two together on Instagram, superimposed with a text that reads: “Brotherhood has no limits.”
Diesel has paid tribute to his late friend several times in the past.
In August he dedicated his Teen Choice Award for “Furious 7” to Walker.