The 57-year-old Australian, who portrayed Queen Elizabeth I in the 1998 film Elizabeth, worked with William on the Earthshot Prize Council, a panel he founded which seeks technological solutions to the climate crisis.
The Hollywood star said he "inherited" his interest from the King, adding that his dedication is evident in how "hands-on" he is.
Speaking to Harper's Bazaar UK, Blanchett said: "(He's been) an extraordinary leader, very hands-on in a consistent and practically engaged way.
"He has inherited that interest (from the King). He's grown up with it."
Blanchett is also a co-founder for the not-for-profit technology company, RSL Media, which operates a register where creatives can log whether they're comfortable having their work scraped by AI companies for machine learning.
"When this technology started to blow up, a lot of the people who were at the cutting edge were going to governments and saying, 'We've done this; how are we going to use it? What the risks?'
"(Everything's) so polarised no one feels they can get around the same table to discuss the challenges, and the central one is consent."
She also commented on the post-MeToo political climate adding that although we are at an "exciting point" there is still a way to go.
"We've never reached equality of pay, and not only has MeToo been rolled back, and super-quickly discredited, but there's a conversation in one of the biggest democracies in the world (the US) about women not having the right to vote because of household voting."
The Australian actress is set to appear in an upcoming UK National Theatre production of Electra/Persona where she and her co-star Nina Hoss will alternate the leading roles each night.
7°C