The phrase "adjoining closet" is correct and usable in written English.
It can be used to describe a closet that is next to or connected to another room or space.
Example: "The master bedroom features an adjoining closet that provides ample storage for clothing and accessories."
Alternatives: "attached closet" or "connected closet".
For those who have pedestal sinks or are looking for a more sophisticated solution, Mr. Babus suggests borrowing space from an adjoining closet and installing a recessed linen tower with a pull-out hamper basket.
The King occupied the "Best bedchamber", a large room with an adjoining closet, directly above the saloon, that led directly from the second floor Great Dining Chamber.
The master has a fireplace, a walk-in closet and an adjoining bathroom.
The master bedroom is on the second level and has two closets and an adjoining bathroom.
Five bedrooms and 5.5 bathrooms includes a master suite with a private terrace, his and hers closets and an adjoining office/library.
The master has a walk-in closet, built-in storage and an adjoining sitting room.
A third-floor bedroom has a walk-in closet with original hardware, and an adjoining storage room.
The hotel lobby, with its chandeliers and red carpets, its grand staircase, is an enormous decorated box; Anderson also favors closets, prison cells, cable cars, train compartments and their adjoining windows and doorways.
Closeted in a stall, she heard a strange voice from an adjoining stall ask, "How are you?" Surprised, she politely replied, "Fine, thank you".
The second floor has a master's bedroom and closet on the west side of the house and four bedrooms, each with an adjoining bathroom, on the east side.
Patrick Alexander, who occupied a cell adjoining Matt's, told the Times he was handcuffed the night after the escape, taken by three guards into a broom closet, punched and had a plastic bag placed over his head while questions were shouted at him.
