This species is characterized by its generally strigose pubescence, shortly branched inflorescences with the axes more often dichasial than monochasial, 5-merous flowers, rather deeply lobed calyx limbs with erect obtuse lobes, corolla tubes 10-18 mm long and 1-2.5 mm in diameter, and capsules 10-35 mm long. The plants here treated as Joosia panamensis were included by both Steyermark and Andersson within the Joosia umbellifera, but Joosia umbellifera is here circumsribed more narrowly. Joosia umbellifera is allopatric and has shallowly lobed calyx limbs and elongated monochasial inflorescence axes. Joosia panamensis is also similar to Joosia ulei of Peru, which has 4-merous flowers and spreading calyx lobes. Joosia panamensis is also similar to Joosia confusa of southern Ecuador and Peru, which has corolla tubs 1-1.2 mm in diameter and capsules 40-50 mm long.
Joosia panamensis shows notable morphological variation in Panama, in particular in calyx size and form and diameter of the corolla tubes. This variation was discussed in some detail by Taylor (2017), who concluded that the plants included in this species could not be subdivided by any features and field work will be needed to understand their systematics.