The station has four island platforms serving eight tracks.
Platforms 1 to 4 are for the Yamanote Line, and 5 to 8 are shared by the Saikyō Line, the Shōnan-Shinjuku Line, and the Rinkai Line.
Ōsaki is one of the stations on the Yamanote Line loop where trains are put into and taken out of service.
It therefore has four tracks (two in each direction) for the Yamanote Line so as not to interfere with continuing trains (trains go several rounds before being taken out).
Chest-high platform edge doors were introduced on the Yamanote Line platforms from 22 December 2012.

There are two sets of ticket barriers: the "north" and "south" gates.
The north gate provides access to the east and west exits, while the south gate provides access to the new east and new west exits.

Unlike most other stations with service from multiple different transport companies, at Ōsaki the Rinkai line and JR services are behind the same fare gates, and it is possible to change between JR and Rinkai lines without exiting and re-entering.
Passengers using Suica or another IC card will be charged the combined fare when they exit.
Passengers holding a Japan Rail Pass and transferring onto the Rinkai line, which does not accept the pass, will need to pay the Rinkai line fare when they exit at their Rinkai line destination.
A similar arrangement applies to passengers travelling through from the Saikyō line to Oimachi or another Rinkai line destination.
The station has four island platforms serving eight tracks. Platforms 1 to 4 are for the Yamanote Line, and 5 to 8 are shared by the Saikyō Line, the Shōnan-Shinjuku Line, and the Rinkai Line. Ōsaki is one of the stations on the Yamanote Line loop where trains are put into and taken out of service. It therefore has four tracks (two in each direction) for the Yamanote Line so as not to interfere with continuing trains (trains go several rounds before being taken out). Chest-high platform edge doors were introduced on the Yamanote Line platforms from 22 December 2012.
There are two sets of ticket barriers: the "north" and "south" gates. The north gate provides access to the east and west exits, while the south gate provides access to the new east and new west exits.
Unlike most other stations with service from multiple different transport companies, at Ōsaki the Rinkai line and JR services are behind the same fare gates, and it is possible to change between JR and Rinkai lines without exiting and re-entering. Passengers using Suica or another IC card will be charged the combined fare when they exit. Passengers holding a Japan Rail Pass and transferring onto the Rinkai line, which does not accept the pass, will need to pay the Rinkai line fare when they exit at their Rinkai line destination. A similar arrangement applies to passengers travelling through from the Saikyō line to Oimachi or another Rinkai line destination.
Ōsaki Station