Brosnahan, who plays the title character in the Amazon show, posted a photo of herself under an umbrella with a thick plastic sheet attached to form a full-length shield.
She wrote: “It looks a little different this year…but we’re back! Working away on @maiseltv Season 4.”
She previously shared a picture from her first costume fitting on September 23, in which she sported a mask with her outfit.
“We’re slowly and safely getting back to it but first costume fitting is in the books.
“Damn, it feels good to be (almost) back.”
The series has previously featured a large number of extras but creator Amy Sherman Palladino, who was previously responsible for Gilmore Girls, has reportedly said they will rely less on extras in the new episodes and instead use CGI to fill out crowd scenes.
Rachel Brosnahan confirms production under way on The Marvellous Mrs Maisel