Johnson is due to star as King Kamehameha the Great, the leader who unified the Hawaiian Islands in 1810, in an upcoming movie from his production company.
Johnson today detailed the emotional impact he felt during the protest, in reply to a tweet thanking him for attending and supporting the cause.
"Embracing and hearing the words of our kupuna brought tears to my eyes too. Why I kept my glasses on:)," he wrote. "I'm optimistic we will accomplish our goals. #maunakea"
Upon arriving at the protest, Johnson spoke while dancers performed hula and chants.
"This is such a critical moment and a pivotal time. Because the world is watching," he said.
He went on to tell reporters: "What I realised today ... it's bigger than the telescope. It's humanity. It's the culture. It's our people, Polynesian people, who are willing to die here to protect this land.
"This very sacred land that they believe in so powerfully."
The protest - which is blocking a road to prevent construction crews from reaching the summit - marked its 10th day.
Hawaii County Mayor Harry Kim, who is the governor's envoy to the protesters, is in the process of organising a meeting with Native Hawaiian leaders.
He voiced his fears there will be a "very splintered community" if he can't get people to work together for what he hopes will be a common goal.
"We do not want this to become the cause of a polarised community. That to me is a main issue here," he told The Hollywood reporter.
The mayor recalled saying a silent prayer after receiving a call from the governor on Monday appealing for his help and hopes he can "do the right thing for the right reasons."
But he has no time frame for when he plans to conclude the talks, just "as soon as possible".
- Additional reporting by Associated Press and Bang Showbiz
