The former X Factor contestants, John and Edward Grimes, have been spending the coronavirus lockdown with actress Tara Reid in Los Angeles.
On Tuesday, the Irish twins posted a video on Twitter, in which one of them can be seen standing atop a car that is driving slowly down the boulevard and holding a Black Lives Matter sign.
They can also be heard chanting: "No justice, no peace."
In another video, the duo applaud from a balcony as thousands of marchers walked down the road.
In a third, captioned “Unity of Hollywood Blvd #BlackLivesMatter” one of the twins can be seen joining hands with protestors in front of cops, while chanting George Floyd's name.
The singers also posted photos from the march, with one twin kneeling holding their sign and taking a knee in front of soldiers on the Hollywood Walk of Fame.
The pair tweeted several messages of support throughout the day, including “Freedom You Deserve” and: “'There should be no more hurt. Keep making your voices heard. Together we stand united. Enough is Enough!”
American Pie star Tara Reid previously revealed the twins are currently living with her in LA.
Reid and the Irish double act first met when they appeared on Celebrity Big Brother together in 2011.
Jedward rose to prominence thanks to the 2009 series of The X Factor, and later represented Ireland at the Eurovision Song Contest.