Alexandra Gardens was planned as a formal garden featuring a fountain at its centre. However, the fountain was not built, and a flower bed was substituted instead. The Gardens were one of the earliest parts of Cathays Park to be developed and were known as both Geometrical Gardens before adopting the name Queen Alexandra Gardens on 26th July 1910.

Several memorials have been placed in Alexandra Gardens, including those for the Spanish Civil War and the Falklands campaign. The main memorial in the Gardens is the Welsh National War Memorial, a circular structure of Portland stone designed by Sir J Ninian Comper.

After the unveiling of the Welsh National War Memorial, alterations were made to the planting around it to provide a fitting setting. The architect recommended planting deep red roses on the outer side of the broad path around the Memorial circle and replacing existing trees with columnar shaped trees such as cypresses. The Chief Parks Officer proposed the removal of acacias and the planting of Incense cedars to harmonize with the memorial.

In Spring 2023, eight Thujas planted by Malcolm Frazer were removed from Alexandra Gardens and replaced by eight Hollies (Ilex x koehneana 'Chestnut Leaf'). The Thujas had grown into various shapes that did not complement the formal site, prompting the replacement with Hollies.