In the clip, which was first shared with Black women's magazine Essence, the Duchess of Sussex encouraged the high schoolers to do something one of her former teachers told her: "Always remember to put others' needs above your own fears."
As she addressed the deaths of George Floyd, Breonna Taylor and many other Black Americans "whose names we don't know," she also told the class to "rebuild" and "lead with compassion" in the months and years ahead.
"You are going to have empathy for those who don't see the world through the same lens that you do, because as diverse and vibrant and open-minded as I know that the teachings of the Immaculate Heart are, I know that you know that Black Lives Matter," she said in the video, which was played during a virtual graduation ceremony.
"What is happening in our country and in our state and our hometown of L.A., has been absolutely devastating. I wasn't sure what I could say to you. I wanted to say the right thing and I was really nervous that I wouldn't, or it would get picked apart. And I realized the only wrong thing to say is to say nothing because George Floyd's life mattered, and Breonna Taylor's life mattered, and Philando Castile's life mattered, and Tamir Rice's life mattered, and so did so many other people whose names we know and whose names we don't know."
Meghan also reminded those watching the clip that rebuilding is a constant process that requires empathy, compassion, listening and action.
"And I know sometimes people say, 'how many times do we have to rebuild?' But we are going to rebuild and rebuild and rebuild until it is rebuilt, because when the foundation is broken, so are we," she also said.
"You are going to lead with love, you are going to lead with compassion, you are going to use your voice. You are going to use your voice in a stronger way than you've ever been able to because most of you are 18 or are going to turn 18, so you're going to vote."
In that clip, Meghan discussed how anti-Black racism has affected her life.
"My name's Meghan Markle and I'm here because I think it's a really important campaign to be a part of," she said. "For me, I think it hits a really personal note. I'm biracial. Most people can't tell what I'm mixed with and so much of my life has felt like being a fly on the wall.
"And so some of the slurs I've heard or the really offensive jokes, or the names, it's just hit me in a really strong way. And, you know, a couple of years ago I heard someone call my mom the N word.
"So I think for me, beyond being personally affected by racism, just to see the landscape of what our country is like right now, certainly the world, and I want things to be better."
She also said she hoped that by the time she had children, "people are even more open-minded about how things are changing, and that having a mixed world is what it's all about." Last year, Meghan and Prince Harry welcomed their son, Archie. The little boy turned one year old on May 6.