The cause began in 1858 as a Sunday School held in various houses until a schoolroom was built and opened on 6 February 1859. 49 members were released from Calfaria, Aberdare to form the new chapel at Gadlys, which was built in 1864 on land leased from Dr J.L. Roberts of Gadlys Uchaf Estate. The architect was Thomas Joseph and the building cost £675. The first Baptism had taken place on 5 April 1863.
The minister from 1876 until his death in 1900 was Benjamin Evans, known as the 'Bishop of Gadlys'.
Twentieth Century
The history of Gadlys in the twentieth century was characterised by a series of comparatively brief ministries, none of which lasted for more than ten years. Myles Griffiths from Bangor College, but a native of Neath was inducted as minister in July 1902 at a service at which William Harris of Heolyfelin presided. He moved to Liverpool in 1906. R.Gwenffrwd Hughes arrived from Valley and Caergeiliog in Anglesey in 1908. During his time at Gadlys,hughes became involved with Liberal Party politics and was nominayed as a candidate for a seat on the Board of Guardians in 1910. although he was not selected. After a brief ministry departed for Pontlottyn in 1910. Shortly afterwards, Hughes was married at Gadlys Chapel to Ethel, daughter of the late Benjamin Evans, the "Bishop of Gadlys". In 1911 the membership stood at 195 although the chapel could seat 600. David Bassett from Penparc, Cardigan, became the next minister in December 1912 and remained for ten years until his death on January 1 1922. J.H. Jones came from Laleston in 1925 and remained for four years before moving to Bonymaen. He was followed by Thomas Richards, a student from Cardiff College who was inducted in 1933 and served for seven years before moving to Kensington Chapel, Brecon, in 1940. A new organ was installed in 1940. Iorwerth Davies moved from lower down the valley at Calfaria, Abercynon, in 1946 and served until 1951. The minister from 1954 until 1957 was Gwyn Rogers.
Later history
The chapel closed in 1980 and was later converted into flats.