Phyllostegia pilosa is a scandent vine or herb in the Lamiaceae (mint) family. Stems are moderately short-haired. Leaves are ovate to elliptic-ovate, 3 to 14 cm (1.2 to 5.5 in) long, 3 to 4.5 cm (1.2 to 1.8 in) wide, lower surface glandular-dotted with short hairs, densely so along veins. Flowers are 6 to 12 per pair of inflorescences that are 7 to 12 cm (2.8 to 4.7 in) long, also with short hairs. The corolla tube is slender and curved, 7.3 to 10 mm long (0.3 to 0.4 in) and lower flower lip is 3.5 to 5.5 mm (0.1 to 0.2 in) long. Fruit not described.