Built by the St. George's Harbour and Railway Company in 1858, this branch line heads north through Deganwy before terminating in the town.

Initially the Conwy Valley line ran into a separate platform on the south side of the station, and a refreshment room was built in 1864.

Three of the platforms on the southern side (both bays and the down loop) were taken out of use in 1968 when the easternmost of the two signal boxes was closed and the track layout altered.

In 1983 the branch junction was again moved slightly eastwards to allow a new freight terminal (now disused) to be built to replace the original goods yard and another at nearby Colwyn Bay that had been closed before the start of the A55 road widening scheme the previous year.

The station was also remodelled once more and resignalled at this time, and in 1985 a new power signal box was commissioned at the western end,[2] which now controls the station area and junctions along with the main line between Colwyn Bay and Conwy and the northern end of the Conwy Valley branch (using the electric token system).

The token machine for the branch is located at the station rather than in the signal box for operational convenience, allowing drivers to collect or return their token (with the cooperation of the signaller) whilst station work is undertaken, rather than having to make an additional stop at the box to make the exchange.