Limited service to Plymouth was provided prior to April 2021 but was cut due to low ridership and budget constraints.

Trains continued southeast from Middleboro to four different termini on Cape Cod: Woods Hole, Hyannis, Chatham, and Provincetown.

In 1935, the bankrupt New Haven attempted to default on its lease and return ownership of the line to the Old Colony stockholders; however, this drove the Old Colony, which had not run trains in over thirty years, to bankruptcy in one day, and the New Haven was forced to run the trains by court order, with a provision that, if losses exceeded a certain amount, they could abandon the line.

The New Haven's accountants used somewhat dubious practices to shift a greater amount of debt to the Old Colony Division, and the railroad announced that all passenger service would end in 1958.

An emergency subsidy was approved by the Commonwealth of Massachusetts for another year, and service finally ended in 1959 with the opening of the Southeast Expressway, which runs alongside the Old Colony right-of-way in many sections.

Both lines received a full restoration for 59 miles per hour (95 km/h) passenger service, including passing sidings and fully handicapped accessible stations with full-length high-level platforms.

Tracks were laid parallel to the Red Line along the original right-of-way, including a new two-track bridge over the Neponset River.

The shutdowns were for the purposes of replacing defective concrete ties (which had begun failing far earlier than expected) with wooden ones.

[5] Tie replacement started in March 2011 and was substantially complete by September, although the full project – which includes grade crossing and bridge work – was expected to take until the summer of 2012.

The move came as a part of fare increases and service cuts in order to close the agency's operating budget shortfall for the following year.

[11] The fork at the end of the Kingston/Plymouth Line (which lacks a wye) creates operational issues – a single train cannot serve both terminal stations efficiently.

[12] In November 2020, as part of service cuts during the pandemic, the MBTA proposed to close Plymouth along with five other low-ridership stations on other lines.

[13] On December 14, the MBTA Board voted to enact a more limited set of cuts, including indefinitely closing Plymouth and four of the other five stations.

[24] In 2007, the Boston Region Metropolitan Planning Organization released a report evaluating the possibility of extending regular full-year commuter rail service to Buzzards Bay (on the north side of the Cape Cod Canal opposite Bourne), including several intermediate stops.

[24] However, other projects (such as the restoration of service on the Greenbush Line) received priority, and the extension to Buzzards Bay was not constructed.

[26] The Buzzards Bay town selectmen similarly supported the idea later that year, and a public forum was held in January 2014.

[29] A Local Impact Report released in April 2015 proposed an 800 foot (240 m) high-level platform and two parking alternatives: a 120-space modification of the existing lot, or a 400-to-600-space structure (including a realignment of Academy Drive).

[29] Bourne voted to join the MBTA district in 2015 and began paying an assessment in mid 2016 (for FY 2017), although there was no guarantee that commuter rail service would be provided in the fiscally constrained environment.