Andrew Woodhouse, 44, from Monmouthshire beat one so badly he suffered two broken legs and a broken arm. He then sat on burglars Kevin Green and Timothy Cross until the police arrived, Cardiff Crown Court heard.
Woodhouse's firm had repeatedly been targeted by thieves. Green and Cross were later fined 75 pounds each for theft.
He was woken around midnight one day in March 2013 by a text message telling him that a burglar alarm had gone off at the tyre yard.
The court was told Woodhouse was arrested and accused of using excessive force.
Also Read
But Andrew Taylor, the lawyer of Woodhouse said: "These thieves thought they would have nice easy pickings that night.
"Many people would have given up and just claimed on their insurance but Mr Woodhouse is made of sterner stuff.
"He showed stoicism, courage and fitness to chase them. One of the men was armed and went to attack him. He acted in lawful self defence," Taylor was quoted as saying by the BBC.
But Woodhouse chased Green and caught him near their getaway car. He attacked Green leaving him with two broken legs and a broken arm.
Woodhouse then chased Cross before rugby-tackling him and then lying on top of the raider until police arrived.
The court heard how Woodhouse gave police a full account of how he fought with the two raiders like a "mad man".
He told police: "I swore at the men and grabbed one of them, I then felt a blow to my hand and shoulder and began grappling with them.
Woodhouse said he was "gutted and sickened" to learn the extent of Green's injuries.
The gardener, who denied the charges and was found not guilty yesterday, had suffered the theft of machinery worth between 15,000 and 25,000 pounds in recent years.