His death was announced through his social media accounts, where it was said Boseman had been diagnosed four years ago.
In Nyong'o's statement, she said she was struggling to think and speak about her friend in the past tense. "The news of his passing is a punch to my gut every morning," she wrote.
"I am aware 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 always be — here ... that seem ageless... Chadwick was one of those people."
She wrote about how he always "commanded his time with ease."
"He showed up to every rehearsal and training and shoot day with his game face on," Nyong'o said. "He was absorbent. Agile."
Nyong'o said Boseman used his body in all the ways that he could, by doing his own stunts, drumming at his own parties, doing martial arts, and he respected his body while doing that. "In so doing, he took the risk to be alive, fully alive," she said. "So it seems that it was life that gave up on Chadwick long before Chadwick gave up on life."
Being around him, she said, made her want to be "be better, less petty, more purposeful."
"He used his life force to tell meaningful stories," she said. "And now we tell his... Chadwick’s death is something that I can neither take in nor take in nor take in my stride right now."
"Perhaps with time… I’m going to take my time… and in his honor, I promise not to waste my time," Nyong'o wrote. "I hope you will do the same."