The Skywalker saga will be completed with the release of the 2019 film, which begins shooting this week.
On Friday it was confirmed that Fisher – who died in 2016 – will be seen courtesy of unused footage she filmed for The Force Awakens.
Hamill tweeted that the news is “bittersweet” as he spoke out on his own return to the saga, after Luke Skywalker was seen appearing to die at the end of 2017’s The Last Jedi.
“It’s bittersweet facing my final chapter without her-She is simply irreplaceable,” he wrote.
“I’m finding solace in the fact that she won’t BE replaced & would love the worldwide outpouring of affection from those who loved her when they heard the news.”
Of his own comeback, which he had been coy on in recent months, he said: “It’s finally fine to admit #ImInIX-Billy Dee @realbdw too-which is long overdue (No one’s ever really gone).
“Now only 17 months of ‘no comment’s when asked about it to avoid revealing details or fueling speculation #SeeYouAroundKids.”
Also back from the legacy cast will be Anthony Daniels as C-3P0.
JJ Abrams is directing the trilogy finale, and said in a statement Friday: “We desperately loved Carrie Fisher.
“Finding a truly satisfying conclusion to the Skywalker saga without her eluded us. We were never going to recast, or use a CG character.”
Todd Fisher, Carrie’s brother, had previously said he thought Leia would be back via archive footage, but this was shot down at the time by LucasFilm president Kathleen Kennedy, who said he was “confused”.
Now, however, Todd has told The Hollwood Reporter: “If I was in anyway an inspiration for the final decision to keep Leia a part of the story, that’s great.
“I must say at times I felt like a voice crying in the wilderness.”
Star Wars: Episode 9 is out in December 2019.