Nyong'o penned a long message about Boseman and the effect he had on her career and the world alongside a black and white image of the pair laughing together.
The actress starred as Nakia alongside Boseman's Black Panther in the Marvel film.
"The news of his passing is a punch to my gut every morning. I am aware that we are all mortal, but you come across some people in life that possess an immortal energy, that seem like they have existed before, that are exactly where they are supposed to be always be - here! ... that seem ageless... Chadwick was one of those people," Nyong'o said.
"Chadwick is a man who made the most of his time, and somehow also managed to take his time. I didn't know him for long, but he had a profound effect on me in the time that I did," she continued.
Nyong'o also mentioned how Boseman was a dedicated actor on set, lived life to the fullest and how he cared for others.
"He cared so deeply about humanity, about Black people, about his people. He activated our pride. By pushing through and working with such high purpose in the films he chose to commit to, Chadwick has made infinite his home," Nyong'o said.
"We are all charged by his work as a result, by his presence in our lives. His power lives on and will reverberate for generations to come. He used his life force to tell meaningful stories. And now we tell his," she continued.
Boseman died in August at the age of 43 after a four-year battle with colon cancer.
The actor also portrayed Black Panther in Captain America: Civil War, Avengers: Infinity War and Avengers: Endgame. Boseman additionally starred as Jackie Robinson in 42, as James Brown in Get On Up and as Thurgood Marshall in Marshall.