The station opened on 1 June 1847 when the Southampton and Dorchester Railway was completed.
The station was built as an east facing terminus with the intent of continuing the line westwards towards Exeter.
These plans were never realised, and instead another line was built from the terminus towards Weymouth.
This joined with the Great Western Railway's line (now the Heart of Wessex Line) from Dorchester West and continued as a joint line to Weymouth.

Originally named Dorchester, the station was renamed Dorchester South on 26 September 1949.
The station remained a terminus with trains from Bournemouth having to enter the station, reverse out back the way they came then reverse again and proceed to Weymouth.
Trains from Weymouth had to pass the station, then reverse into it, and then back out.
This process often caused delays and brought criticism following an accident in 1877.
As a result, a curved platform was provided for southbound trains; this was brought into use during 1878.
Eastbound trains still reversed into the original platform until 1970 when a platform was built on the curve.
The buildings on the trackless original platform remained in use until 1989.
As part of the modernisation work preparatory to electrification a new booking hall was built on the curved platform, replacing the building on the original platform which was then demolished.
The station opened on 1 June 1847 when the Southampton and Dorchester Railway was completed. The station was built as an east facing terminus with the intent of continuing the line westwards towards Exeter. These plans were never realised, and instead another line was built from the terminus towards Weymouth. This joined with the Great Western Railway's line (now the Heart of Wessex Line) from Dorchester West and continued as a joint line to Weymouth.
Originally named Dorchester, the station was renamed Dorchester South on 26 September 1949. The station remained a terminus with trains from Bournemouth having to enter the station, reverse out back the way they came then reverse again and proceed to Weymouth. Trains from Weymouth had to pass the station, then reverse into it, and then back out. This process often caused delays and brought criticism following an accident in 1877. As a result, a curved platform was provided for southbound trains; this was brought into use during 1878. Eastbound trains still reversed into the original platform until 1970 when a platform was built on the curve. The buildings on the trackless original platform remained in use until 1989. As part of the modernisation work preparatory to electrification a new booking hall was built on the curved platform, replacing the building on the original platform which was then demolished.
Dorchester South railway station