He's used his first tweet in more than 18 months to raise awareness on an issue dear to his heart the only way celebrities know how - by gathering a massive clan of famous people to talk to the camera, and you, gentle viewer.
While they never mention him by name, it's a video clearly taking aim at Donald Trump.
You know that because Don Cheadle called this unnamed guy a "racist, abusive coward who can permanently damage the fabric of our society" while others questioned whether it was a good idea to "give nuclear weapons to a man whose signature move is firing things?".
The video includes Whedon's Avengers superstars such as Robert Downey Jr, Scarlett Johansson, Mark Ruffalo and Cheadle, plus other Hollywood types such as James Franco, Julianne Moore, Keegan-Michael Peele, Stanley Tucci, Randall Park, Bradley Whitford and Rosie Perez.
And because it is Whedon, there are plenty of other Whedonverse actors such as Nathan Fillion, Tom Lenk, Ashley Johnson, Clark Gregg, Neil Patrick Harris, Cobie Smulders and Clea Duvall (who was in an episode of Buffy in season one, so she counts, OK?).
The best part may actually be the appearance of the most popular US president in (ahem, TV) history, Josiah Bartlet. Oops, we mean Martin Sheen.
In typical Whedon style, the message is a mix of humour and pathos. We can't do credit to it. You'll have to watch it yourself to be bathed in the full Whedon glory. There's also a pledge to make Ruffalo do a nude scene ("full frontal") in his next movie if Trump is kept from the Oval.
It's not the first time Whedon has waded into a presidential election with a snarky video. Last election cycle, he created a PSA about why it was essential America elect Mitt Romney so the zombie apocalypse can begin.
Whedon quit Twitter last year after a divided reaction to the story arc of the Black Widow character in his Avengers sequel. He became the target of a campaign on social media which lobbed sexism accusations at a man well-known for his feminism credentials.