Yes, Mayuri does have a mask. He is one of the most distinctive characters known for hiding behind a mask, which contributes to his unique and often unsettling appearance.
Mayuri Kurotsuchi's aesthetic is a defining feature of his character. He is noted for his highly unusual and "weird-looking" appearance, consistently adopting new forms that are even "scarier and more gothic" than the last. His use of a mask is a consistent element across these numerous transformations, serving as a key part of his ever-changing, yet always bizarre, presentation.