Male Zeltus amasa has black upper wings, baso-dorsal area of the forewings and hind wing area except apical are pale blue. The female species is pale brown in color with a whitish tornal area marked by marginal black spots on the hind wings. The underside of the wings are white with reddish brown apical area of the forewings. The hind wings have small black spots at the base of space 7, large black spots in space 2, and one black spot in the tornal lobe, there are two pairs of long white tails at the end of the 1st vein, shorter at the end of 2nd vein.
Larva: Zeltus amasa larvae are yellowish green in color, their surface is covered by short and smooth setae.
Pupa: The pupa of Zeltus amasa is greenish in color with two yellowish green patches on the dorsal, one on the thoracic segment and the other on the abdominal segment. There are a pair of brown spots on the thoracic area, while on the abdominal side there are two rows of brown spots. The pupa forms sideways, unlike lycaenids in general which are elongated.