The British actress took part in the project, which was aimed at eschewing self-promotion or commercial content in favour of calling for racial equality, by posting a black square on social media.
While she received praise from many fans, some accused the 30-year-old of performative activism and pointed out her squares had white borders, fitting in with the rest of her Instagram posts.
The Little Women star then shared a number of anti-racism resources, saying she had waited for Blackout Tuesday to finish in the UK before posting again.
Watson wrote: “There is so much racism, both in our past and present, that is not acknowledged nor accounted for. White supremacy is one of the systems of hierarchy and dominance, of exploitation and oppression, that is tightly stitched into society.
“As a white person, I have benefited from this. Whilst we might feel that, as individuals, we’re working hard internally to be anti-racist, we need to work harder externally to actively tackle the structural and institutional racism around us.
“I’m still learning about the many ways I unconsciously support and uphold a system that is structurally racist.”
Watson said she will be using her social media accounts to share links to resources she has found “useful for my own researching, learning, listening.”
She added: “I see your anger, sadness and pain. I cannot know what this feels like for you but it doesn’t mean I won’t try to.”
Watson, known for playing Hermione Granger in the Harry Potter films, also posted artwork and poetry from American artist Fahamu Pecou.
Her posts came as mass protests continue to rage across the US and elsewhere following the death of George Floyd, a black man who died in police custody.
An officer who was filmed with his knee on Floyd's neck for over eight minutes has been charged with his murder
Numerous famous faces have spoken out about Black Lives Matter and race-related conversations, with Alison Hammond winning praise for an emotional speech she gave on This Morning.
Clara Amfo also spoke candidly on Radio 1, telling listeners that she had been off-air on Monday as her mental health was in a "really, really bad way."
Additional reporting by Press Association.