This species is characterized by its medium-sized elliptic leaves, racemiform inflorescences with rather stiff peduncles and primary axes and fewer than a dozen or more flowers, reduced lobed involucels, pedicels 0.5-5 mm long, shortly lobed calyx limbs, red pink corollas with tubes 7-10 mm long and the lobes strongly reflexed and winged pyrenes. The corolla tubes are shorter than the lobes. The full range of pedicel length is usually found on an individual inflorescence, which Cortés-Ballén (2003) noted is unusual in Retiniphyllum. Cortés-Ballén (2003) reported the corolla tubes as 11-14.5 mm long, but these are 7-10 mm long on all the specimen seen of this species including paratypes and material identified by her. She noted (2003: 193) that one of the specimens originally included in Retiniphyllum maguirei is actually Retiniphyllum laxiflorum, which has corolla tubes of about that length; perhaps this measurement confusion is based on that specimen.

Steyermark (1965) separated two varieties of Retiniphyllum maguirei based on size, pubescence, and degree of lobing of the calyx limb and development of the higher order venation on the lower leaf surface. Cortés-Ballén (2003) however noted that these characters are continuously variable, and did not recognize infraspecific taxa for this species.

Retiniphyllum maguirei is similar to Retiniphyllum tepuiense, of premontane and montane vegetation in the Guayana Highlands and the Andes; Retiniphyllum tepuiense has inflorescences with a dozen or more flowers and white to pink corollas with tubes 4-7 mm long.