Stroll is departing Williams, and Kubica is his replacement, where the returning F1 driver will be alongside George Russell, for his rookie season in the competition.
Williams finished rock-bottom of the constructors' championship in 2018, with just seven points secured all season - six of them from Stroll.
Kubica is completing a remarkable comeback to F1, after an eight-year absence from the sport following severe hand injuries from a rally-car crash.
"Robert's been very helpful," Stroll told Crash.net, with the Canadian joining Racing Point for the 2019 campaign. "He just has a good view on things and he's very passionate. I wish him all the best for (2019).
"His recovery's been incredible, what he's been through I couldn't even imagine. It's great to see him back on the grid. I'm sure the team can turn things around and I'm sure that he'll be a big help."
Stroll is joining Racing Point, formerly Force India, seemingly because of his father - Lawrence Stroll; who has took over the team after saving them from administration.
The young Canadian will drive alongside Sergio Perez in his first season with the British-based team.