The wrestler-turned-Hollywood star made the difficult decision to put his beloved pet to sleep after Brutus was poisoned by a mushroom while playing outdoors.
In a heartfelt post to Instagram, the star said: " Another reminder we have to live and love as greatly as we can today, because tomorrow is never guaranteed.
"At approximately 11:15pm last night myself and @laurenhashianofficial had to make the painful decision to end Brutus' suffering by taking him off of life support and sending his soul to pup heaven. I held his lil' paw as he was finally at peace.
"As all puppies and dogs do, he ate a mushroom while playing outside with his brother Hobbs. This mushroom happened to have a lethal toxicity and within hours it was rapidly destroying his liver and immune system to the point of no return.
"I encourage all of you out there to be mindful of mushrooms in your yards, parks or anywhere outside your dogs play. What looks innocent, can be deadly to your lil' family members. Thank you Dr. Deckelbaum and Dr. West and the incredibly caring nurses and staff at The Animal Medical Centre At Cooper City.
"We'll always love you Brutus.. and you'll always be my lil' main man and rough housing Brute.
The Rock's final comment was a reference to how he saved Brutus from drowning just three weeks ago in an incident that happened just as he adopted the tiny dog.
At the time, he told fans: "We just decided to add two new members to our Johnson family. Baby French Bulldogs. In my right hand is BRUTUS and in my left hand is HOBBS.
"Bring them home and immediately take them outside so they can start learning how to "handle their business and potty like big boys". I set them both down and they both take off in a full sprint and fall right into the deep end of our pool. HOBBS immediately starts doggy paddling while BRUTUS (like a brick) sink heads first to the bottom of the pool.
"I take off into a full sprint, fully clothed, dive in the pool, swim to the bottom, rescue my brick, I mean BRUTUS and bring him back to the edge of the pool. He was a little delirious.. took a moment, threw up all the water he swallowed and looked up at me as if to say, "Thank God you didn't have to give me mouth to mouth!" and then ran off to play with his brother.
"A few lessons I've learned today.. A) Not all puppies have the instinct to doggie paddle. B) Some puppies (like BRUTUS) will be so in shock by experiencing water they will sink extremely fast so react quick. C) While spiriting to save your puppies life, before you dive in, try and throw your cell phone to safety. Don't keep it in your pocket... like I did."