Horse Sand Fort was designed by Captain E. H. Stewart, overseen by Assistant Inspector General of Fortifications, Colonel W. F. D. Jervois.

Construction work began in 1865, and the fort was completed in 1880, long after the threat of a seaborne invasion from France had passed, at a cost of £424,694.

Beginning in 1908, extensive submerged defences were built in the form of large concrete blocks running about 1.8 metres (5.9 ft) below sea level from the fort to the shore at Southsea.

[3] With only two narrow gaps[4] to allow small craft to pass through, this barrier (and a much shorter one running south from No Man's Land Fort towards Ryde Sands) remains as the cost of demolition is deemed too high.

[9] An October 2018 report stated that restoration work on Horse Sands Fort was delayed "by the presence of a resident family of peregrine falcons".

A news item stated that Horse Sand Fort was "a blank canvas, with 100 chambers and living quarters, plus the original gun carriage".