Starting in Sisseton, SD 127 runs north for 13 miles (21 km), then turns east at the eastern terminus of SD 106 where it runs east for 19.1 miles (30.7 km).

Turning to the north, SD 127 passes on the east side of White Rock Colony before entering North Dakota as ND 127.

The old route from I-29 to the North Dakota state line near White Rock was designated as SD 127.

In 1984, when construction of I-29 between Peever and New Effington was completed, this segment of US 81 was also routed onto it, and SD 127 was extended along its former alignment, to SD 10 east of Sisseton.

[citation needed] The entire route is in Roberts County.