This species is characterized by its shortly petiolate, somewhat robust, elliptic leaves, its very short ovate to triangular stipules with numerous densely grouped glands, its pedunculate cymose inflorescences with the axes subverticillate and the flowers subessile in several small groups, its shortly deeply lobed calyx limbs with narrow acuminate lobes, its medium-sized flowers, and its fruits that are markedly depressed-ellipsoid. Rudgea crassipetiolata is generally similar to Rudgea clerodendroides and Rudgea hispidula, and these see, to be separated most reliably by calyx form, with the calyx lobed for half or less and the lobes triangular to broadly so in these other two species. Some specimens of Rudgea from Peru have been identified as Rudgea crassipetiolata and have the robust leaves and fruits that characterize this species but have a subtruncate to very shallowly lobed calyx limbs with broadly triangular lobes (e.g., E. Rodríguez et al. 1156), and thus do not match the characterization of Rudgea crassipetiolata in the protologue, nor its separation there from these other two species. These Peruvian specimens are provisionally here included in Rudgea hispidula pending clarification of these three species; they have a calyx limb ca. 1.5 mm long and subtruncate to shallowly, generally evenly lobed.

Rudgea crassipetiolata and Rudgea hispidula have been confused with Ixora rudgeoides, which is sympatric.