The 56-year-old star, who plays the titular character in the movies, arrived at Berlin's Potsdam Babelsberg studios on Wednesday (7 April).
Wrapped up in a hat and scarf, Reeves locked his car and headed into work looking very cheerful indeed as the cast and crew prepare to start photography for the action thriller.
According to reports, development on John Wick 4 began shortly after the third film - John Wick: Chapter 3 - Parabellum was released in 2019.
Speaking to Collider last April, the film's director Chad Stahelski said that the creative team had set the bar much higher.
He said: "We submitted an idea or thematic [plan] and it was really big. So, we're talking about doing a little bit more than a [John Wick 4], or something like that, and trying to develop that."
He went on to tell the outlet: "I'm in a happy place where we are in development...we're in a place where we know what we want do and where we want to do it."
It seems Reeves just wasn't ready to leave his character, as Stahelski explained: "Then we just kinda met each other when we were doing the publicity tour and I think we were in Japan, and Keanu goes, 'I think I got one more left in me,' and we had one idea we didn't use which we really loved and we have to cut it out of number three, just didn't have the space for it.
"So we're like, 'Okay, we'll do a fourth. That's gonna be awesome. We'll make a plan.' The studios went, 'We totally get what you're trying to do.'"
The fourth film isn't due to be released until 27 May 2022 after it was pushed back a year due to the coronavirus pandemic. It was originally due to hit our screens on 21 May 2021 but Keanu Reeves needed to finish filming The Matrix 4 first.
Chad Stahelski told Collider: "I mean, Matrix was only four weeks in when this all happened. So, Keanu's gotta go finish his commitment up on The Matrix, which is a big deal and which I think will probably take him until the end of the year.
"Then we have to go into our prep mode and then we'll start. So release dates, I'm sure with every production from Dave's stuff to our stuff, who knows right now."
Lionsgate later announced the 27 May 2022 date for release.