Caryophyllia smithii is a solitary species of coral with a cup-shaped corallum (stony skeleton) with an elliptical base and a diameter of up to 25 mm (1 in).

The septa (vertical radial calcareous plates) are arranged in four to five cycles and have smooth edges.

The polyp is translucent and the colour is variable and may be white, pink, orange, red, brown or bright green.

[4] The habitat of Caryophyllia smithii is often dominated by sponges and bryozoans and these also grow on the corallum of the coral.

The larvae of the barnacle Megatrema anglicum often settle near the rim of the corallum where they appear to be immune to the coral's nematocysts.