The road has many towns on its route including Rotherham, Maltby, Gainsborough and Market Rasen.

The road then passes under the M1 on the lower deck of the Tinsley Viaduct as a dual carriageway with the Meadowhall Shopping Centre visible to the southwest.

The road enters the borough of Rotherham at a bend to the left, becomes the parish boundary between Brinsworth and Rotherham, and there is a crossroads, with the left for Balk Lane and the BOC Brinsworth Operations Centre, opposite Firth Rixson Aurora Sports Club, and the right for Bonet Lane (B6067) near The Fairway.

The road then serves as a bypass of Rotherham after it combines with the dual-carriageway Centenary Way (A630) at Canklow Roundabout.

It continues to the south-east as the non-trunk dual-carriageway West Bawtry Road, with Canklow Woods to the east, on the side of the Rother Valley.

Canklow Meadows Industrial Estate is on the right with Leger Holidays HQ, the large Crossroads Volvo truck garage, and Manheim Auctions.

It is followed by the Canklow Meadows Retail Park, and it passes the Holiday Inn Rotherham-Sheffield on the left (former Swallow Hotel), opposite Energy Alloys.

The A631 used to continue to the east as a trunk single-carriageway, but was upgraded to dual carriage way to the A618, and is crosses by the Rotherham Roundwalk.

The West Bawtry Road Improvement – Rotherway to Whiston Crossroads was built by Birse Civils of Barton-upon-Humber for £5 million.

[citation needed] The A631 then continues round Rotherham crossing the A618, becoming the dual-carriageway East Bawtry Road.

After the roundabout is the Rotherham Premier Inn, and The Brecks Beefeater pub on the left, opposite an Esso garage.

It crosses a railway and Scotch Spring Lane (the Doncaster-Rotherham boundary), for Stainton, is on the left, the point where the road becomes the Doncaster-Rotherham boundary for one mile, just before being crossed by a 400 kV pylon line, the point where it also enters the Doncaster postcode.

The road passes along Castle Gate and a JET garage, and at the Market Place, the A60 continues straight ahead, and the A631 leaves sharply to the right at a T-junction for Sunderland Street.

Further on the B6045 joins from Blyth at Drakeholes, where the road has been diverted to the north, over the Chesterfield Canal and Cuckoo Way.

There had been a terrible crash at 11.15am on Tuesday 16 April 1968 at the A631 level crossing, which made national news, where five occupants were killed, including three children.

It was the 10am York to Great Yarmouth train, and the level crossing was a new automatic half-barrier, which had been installed 18 months earlier.

The driver of the car was John Hilton, aged 50, manager of the New Charnwood Restaurant at Blyth, Nottinghamshire, with his two sons Stuart, 8, and Irvine, 9, and his daughter Sheena, 13, and with his mother-in-law Maria Moody.

It passes The Bell and becomes the parish boundary between Osgodby (to the north) and West Rasen (to the south).

The road becomes more twisty and meets a roundabout at West Rasen, where it crosses the River Rase.

It meets the B1202 (former A46) from the left, and as Queen Street passes under the Newark to Grimsby Line then is crosses by the B1203 at traffic lights.

As Willingham Road it passes the De Aston School and Market Rasen Racecourse on the right.

It then ascends the western edge of the Lincolnshire Wolds as Willingham Road to 142 metres height, crossing Caistor High Street (B1225) at Boucherette Farm, where it enters East Lindsey.

It passes through South Elkington, where in the parish of Elikington it terminates at the A157 just outside Louth (53°21′55″N 0°02′02″W / 53.3652°N 0.0339°W / 53.3652; -0.0339 (A631 road (eastern end))).