The name Yokosuka line is used both for the official railway line Ōfuna - Yokosuka - Kurihama and for the train service running Tōkyo - Yokohama - Ōfuna - Yokosuka - Kurihama.

At Tōkyō station, Yokosuka line uses an underground station connected with Sōbu line.
Between Tōkyo and Shinagawa, Yokosuka line runs underground parallel to Tōkaidō and Keihin-Tōhoku lines, stopping only at Shimbashi.
Between Shinagawa and Yokohama, Yokosuka line uses a section of the Tōkaidō line called Hinkaku line. Yokosuka line and Shōnan-Shinjuku line between Nishi-Ōi and Yokohama are the only services using the Hinkaku line.
Between Yokohama and Ōfuna, Yokosuka line runs on a dedicated double track parallel with Tōhoku line. At Hodogaya and Higashi-Totsuka stations, it's only the Yokosuka line tracks which have platforms.

The line is used by the Yokosuka line service and by the Shōnan-Shinjuku line service.

There are no passenger platforms at Tsurumi station. All trains continue into Yokohama using a dedicated double track.

Between Tōkyō and Shinagawa, the Yokosuka line tracks are also used by Narita Express trains bound for Shinjuku. They run between Shinagawa and Shinjuku and tracks known as "Yamanote freight line" parallel to Yamanote line.