On December 9, 2007, an express service began to run on Line 4 at peak times, stopping at certain stations only to allow for faster journeys.

On June 1, 2018 Chilean President Sebastián Piñera announced in the public account the extension of Line 4 to the sector of Bajos de Mena in Puente Alto that will be operational in 2026.

In October 2019, as a result of the protests caused by the rise in the subway fare, major damage occurred throughout the metro network.

The Los Quillayes, San José de la Estrella, Macul, Protectora de la Infancia, Trinidad and Elisa Correa stations were completely burned; the latter two stations suffered the worst amount of damage to their structures and tracks, which would prevent normal operation of Line 4 for a period lasting 10 to 12 months.

On November 6, the electrification of the tracks in the section between the stations Las Torres and Plaza de Puente Alto was restored, which suffered considerable damage, while evaluating the repairs to the line.

Another proposal is considering connecting the Huechuraba business district with Tobalaba station, passing under the Costanera Center and San Cristóbal Hill.