The 6000 Series cars were delivered in 1998 for service on Line 9. These were the first Madrid Metro cars to have an articulated joint allowing for passage between train cars without needing to exit the train. However, the 6000 Series cars only had one articulated joint in each pair of cars, meaning that the trains are in married pairs and not complete six car trainsets. The 6000 Series also featured suburban style seating for passengers traveling on the suburban section of the line to stops between Puerta de Arganda and Arganda del Rey. These were also the first Madrid Metro cars to have exterior destination signs and electronic run number signs. The reason for this was that Line 9 was the first line with multiple segments so it was considered helpful to display the destination on the train's exterior. These trains also operated on Line 7.

In 2013, 73 of the 108 6000 Series trainsets were sold to the Buenos Aires Underground for use on that system's Line B. As of 2018, the 6000 Series cars that remain in Madrid operate on Line 9 between Puerta de Arganda and Arganda del Rey.