Construction commenced on 1 March 1884.
There was a breaking through ceremony on 17 July 1886; and the official opening was held on 16 January 1888.
During construction the tunnel entrance had a crimson streamer stretched across it with the Latin phrase Labor omnia vincit, meaning, Hard work conquers all.
A 180-metre (600 ft) hill rises above the tunnel.
Construction took place without cessation, night and day, excepting only upon Sundays; and approximately 300 men were employed in the excavation works; and over 91 tonnes (100 short tons) of gunpowder and 9.1 tonnes (10 short tons) of dynamite.
Perforation work for the tunnel was provided via by ten percussion rock-drills using by compressed air obtained from a 30-kilowatt (40 hp) engine.
Approximately 95,200 cubic metres (124,500 cu yd) of rock were excavated and approximately 10,000,000 bricks were laid, supplied by Gore Hill Brickworks.
No less than 10,000 cement casks were used.

Flooding of the area occurred in 1887, resulting in an inspection of the site by Henry Deane,
The Herald reported:
15 November 1887, Mr. H. Deane, inspecting engineer of the Railway Department, returned to Sydney from an inspection of the Woy Woy tunnel.
It was revealed that a creek which passes over a portion of the tunnel was swollen by an unusually heavy rainfall.
The water forced its way through the creek bed, around a portion of the tunnel lining and found an outlet through the weep-holes of the masonry work.
No damage was done to the tunnel.
To prevent the possibility of any future problems arising, it was proposed to temporarily channel the creek over the tunnel using flumes, whilst constructing a permanent solution.
Construction commenced on 1 March 1884. There was a breaking through ceremony on 17 July 1886; and the official opening was held on 16 January 1888. During construction the tunnel entrance had a crimson streamer stretched across it with the Latin phrase Labor omnia vincit, meaning, Hard work conquers all. A 180-metre (600 ft) hill rises above the tunnel. Construction took place without cessation, night and day, excepting only upon Sundays; and approximately 300 men were employed in the excavation works; and over 91 tonnes (100 short tons) of gunpowder and 9.1 tonnes (10 short tons) of dynamite. Perforation work for the tunnel was provided via by ten percussion rock-drills using by compressed air obtained from a 30-kilowatt (40 hp) engine. Approximately 95,200 cubic metres (124,500 cu yd) of rock were excavated and approximately 10,000,000 bricks were laid, supplied by Gore Hill Brickworks. No less than 10,000 cement casks were used.
Flooding of the area occurred in 1887, resulting in an inspection of the site by Henry Deane,
The Herald reported:
15 November 1887, Mr. H. Deane, inspecting engineer of the Railway Department, returned to Sydney from an inspection of the Woy Woy tunnel. It was revealed that a creek which passes over a portion of the tunnel was swollen by an unusually heavy rainfall. The water forced its way through the creek bed, around a portion of the tunnel lining and found an outlet through the weep-holes of the masonry work. No damage was done to the tunnel. To prevent the possibility of any future problems arising, it was proposed to temporarily channel the creek over the tunnel using flumes, whilst constructing a permanent solution.
Woy Woy Tunnel