Trimeresurus popeiorum may grow to a total length of 770 mm (30 in), which includes a tail length 170 mm (6.7 in).

Above green, below pale green to whitish, the two separated by a bright bicolored orange or brown (below) and white (above) (males) or white (females) ventrolateral stripe, which occupies the whole of the outermost scale row and a portion of the second row.

Dorsal scales in 21 (rarely 23) longitudinal rows at midbody; 9-11 upper labials, first upper labials separated from nasals by a distinct suture; a single supraocular.
Ventrals 155-169; subcaudals 52-76, in males the base of the tail enlarged to the level of subcaudals 20-25; hemipenes long and slender, smooth, without spines.

This species is most often confused with T. s. stejnegeri (q.v.);
the two have quite distinct hemipenes, which does not make identification of individuals in the field or in the laboratory any easier without recourse to (a) male individuals and (b) an examination of the hemipenes.
However, the two species are not known to have overlapping distributions, at least based on available materials.
Also, closely allied to T. popeiorum is Trimeresurus yunnanensis (q.v.);
ordinarily, the two are more easily told apart by the number of midbody dorsal scale rows, 21 in T. popeiorum, 19 in T. yunnanensis.
Trimeresurus popeiorum may grow to a total length of 770 mm (30 in), which includes a tail length 170 mm (6.7 in).
Above green, below pale green to whitish, the two separated by a bright bicolored orange or brown (below) and white (above) (males) or white (females) ventrolateral stripe, which occupies the whole of the outermost scale row and a portion of the second row.
Dorsal scales in 21 (rarely 23) longitudinal rows at midbody; 9-11 upper labials, first upper labials separated from nasals by a distinct suture; a single supraocular. Ventrals 155-169; subcaudals 52-76, in males the base of the tail enlarged to the level of subcaudals 20-25; hemipenes long and slender, smooth, without spines.
This species is most often confused with T. s. stejnegeri (q.v.); the two have quite distinct hemipenes, which does not make identification of individuals in the field or in the laboratory any easier without recourse to (a) male individuals and (b) an examination of the hemipenes. However, the two species are not known to have overlapping distributions, at least based on available materials. Also, closely allied to T. popeiorum is Trimeresurus yunnanensis (q.v.); ordinarily, the two are more easily told apart by the number of midbody dorsal scale rows, 21 in T. popeiorum, 19 in T. yunnanensis.
Trimeresurus popeiorum