Microfilaria panamensis McCoy, 1936 was identified in the blood of Cebus apella, C. capucinus, C. albifrous, and Saguinus oedipus from various regions in Colombia. Adult worms, recovered from the subcutaneous connective tissues of C. apella and S. oedipus, were identified with this microfilaria and are described as Tetrapetalonema (T.) panamensis (McCoy, 1936) comb. n. This nematode is smaller configuration of the female tail and in the appearance of the spicules, and T. barbascalensis which differs in the placement of the vulva relative to the base of the esophagus and in the structure of the right spicule. The spicular ratio of T. panamensis (1.6 to 2.1) is lower than that of any other member of the subgenus (2.6 to 10.8). The host induced and/or geographic variation of microfilariae and adults of T. panamensis is discussed.