The Avengers actress was "so f****** happy" to see her co-star "thriving" as he continues to recover from his devastating snowplough accident at his home in Nevada on New Year's Day which saw the 52-year-old actor suffer blunt chest trauma and orthopaedic injuries.
She told Variety: "I was honestly so f****** happy to see him. I didn't know if I was ever going to see him again.
"To not only see him again but to see him thriving and in such an amazing space, mentally.
"He's a very spiritual person in general and a very soulful person. And you can see that in his work. It comes through. He has such a depth to him.
"And I just was so happy to see that he is full of life and light, and he's also hilarious. We laughed a lot."
Johansson was speaking alongside Chris Evans - who has also appeared in the Marvel Cinematic Universe alongside Renner - and he admitted their reunion was a joyous experience.
He added: "No tears at all. A lot of laughs and smiles and hugs. Leave it to Jeremy to take something this potentially tragic and turn it into something so inspiring."
Johansson was "very upset" when she first heard about Renner's accident, which saw him suffer more than 30 broken bones and needed multiple surgeries after being run over by the snowplough as he tried to save his nephew as the vehicle headed for him.
In the Avengers group chat - which includes the trio along with Robert Downey Jr, Mark Ruffalo and Chris Hemsworth - they have hailed him as a real life superhero.
She said: "On the Avengers text chain, we're like, 'OK, you beat us all. That's it. You won'. That's like real superhero stuff. It's unbelievable."