[2] The line is single-tracked between Kōhoku and Isahaya stations due to the coastal geography of the area making double-tracking prohibitively expensive.

The line was electrified in 1976, however due to the lack of freight trains running beyond Nabeshima and low population along the line, the section between Hizen-Hama and Nagasaki is scheduled to be de-electrified after the opening of the Nishi Kyushu Shinkansen.

Prior to the opening of the new Shinkansen line, limited express trains travelled over the new route between Isahaya and Urakami stations.

Legend The Kyushu Railway Co. opened the Tosu - Saga section in 1891, extending it to Nagasaki via Haiki in 1898.

The 6173m Shin-Nagasaki tunnel and associated Kititsu - Urakami deviation opened in 1972, and the entire line was electrified in 1976.

In January 2022, it was announced that the Nagasaki Main Line would be split into two sections and upper and lower management separation is to be introduced.

As de-electrification means the joyful train "36 plus 3" will no longer be able to reach Nagasaki Station, a new diesel joyful train "Futatsuboshi 4047" is to operate along the Nagasaki Main Line during the morning run and Omura Line in the afternoon return run.