The 26 year-old, who won the super-heavyweight title in 2012, watched on as Joyce lost out to Tony Yoka of France despite seemingly doing enough in the at least two of the three rounds.
After the fight and during his appearance as a BBC Olympic pundit, Joshua was clearly disappointed as he gave his thoughts to John Inverdale with Joyce listening in.
“I’ve never seen a lightweight, let alone a heavyweight throw so many punches in a fight before,” said Joshua.
“Talking about counter-punching and aggressive, Joe was aggressive and making the fight.
“The power that he possesses, there’s no way you can block those shots. He’s penetrating gloves and penetrating body.
“For me, he’s Olympic champion. In spirit he’s champion and he’s done so well. As much as I want him to have the medal, I’m so proud of what’s he achieved.
“The sky’s the limit and he’s a credit to the sport, in and out of the ring. It’s like you’ve got to knock them out at super-heavyweight,” he added.
Joyce, 30, could still make a hefty paycheck if he decides to turn pro and should brace himself for offers as the Briton certainly was the most entertaining of the big men at the Games in Brazil.
Turning late to the sport at 22, Joyce had steadily built towards what was supposed to be his defining moment, although it was Yoka who celebrated ahead of his post-Rio wedding to Women’s lightweight champion Estelle Mossely.