The Baptist cause in Pwllheli was established in 1815, with Bethel Baptist Chapel being built on Pentre Poeth/North Street the following year. 

Photographs taken by the Royal Commission in the 1950s show a long-wall chapel built of rubble stone, the façade facing south away from the road. Built in a very simple, vernacular style, it had two plain, square-headed, doorways - one to each outer bay - with two 'pulpit' windows to the centre. These were both 12-over-12 tall sashes. The doors led directly into the chapel auditorium. Internally the tub pulpit sat against the front wall, between the two windows, with a small sedd fawr and box pews in front, and three further banks of box pews to the centre and side of the ground floor. A three-sided canted gallery was supported on four cast-iron columns and accessed from staircases within the auditorium on either side wall. There was a simple panelled gallery front and panelled box pews with ogee-curved ends, the gallery lit by two tilting small-paned windows to the top of each end gable. On the front of the gallery was stencilled the date 1816. The roof was open to the rafters with king-post trusses. 

The Religious Census of 1851 records that 190 may sit in the seats; 50 to 60 may stand and sit on the benches. The average congregation over the previous 12 months had been 175, with 130 scholars. 

The chapel is associated with Tabernacl Baptist Chapel (NPRN 6801) which was built in 1861 as a larger worship space in the heart of Pwllheli. By the 2nd Edition OS mapping of 1900, Bethel is marked as 'Sunday School'.

The Cadw listing description of 1989 said that the chapel  was 'said to retain a total immersion baptistry', though the chapel had gone out of use in the 1960s and was at that time in use as a store/warehouse. There was a small, triangular graveyard to the front and a single storey rubblestone building attached to the east which is not clearly enough visible in the photographs to discern its purpose. 

By 1998 it was disused, and by 2003 it had been converted into a house with the windows enlarged and replaced and further windows inserted in to the rear wall. The chapel was delisted by Cadw in 2019.

S Fielding RCAHMW May 2025