Nepenthes jamban is a climbing plant.
The stem, which is usually less than 5 mm thick, grows to 4 m in length and is cylindrical-angular in cross section.
Internodes are up to 5 cm long.

Leaves are sessile and coriaceous in texture.
The lamina may be narrowly obovate to elliptic or slightly spathulate, and grows to 11 cm in length and 3.3 cm in width.
One or two longitudinal veins are present on either side of the midrib together with numerous pinnate veins.
Tendrils are up to 24 cm long.

Rosette and lower pitchers are cylindrical to narrowly infundibular in the lower
third, becoming widely infundibular above.
They are relatively small, rarely exceeding 5.8 cm in height and 4.4 cm in width.
Fringed wings (≤2 mm wide) are usually present in terrestrial pitchers.
The pitcher mouth is almost horizontal.
The inner surface of the pitchers is glandular throughout.
The flattened peristome may be up to 8 mm wide and is lined with a series of teeth (≤0.5 mm long) on its inner margin.
The lid or operculum is narrowly obovate, and up to 3.8 cm long and 1.3 cm wide.
The undersurface of the lid bears scattered small red glands that are concentrated around the midrib.
Around 20 to 30 very large crater-like glands (≤0.5 mm wide) are present in the apical quarter.
These glands are so large that they are visible as swellings on the upper surface of the lid.
The spur (≤4 mm long) is inserted at the base of the lid.
It is generally unbranched but may be forked.

Upper pitchers are circular in cross section and widely infundibular in their upper half.
They are much larger than lower pitchers, reaching 12 cm in height and 5.2 cm in width.
The pitcher mouth is horizontal and orbicular.
As in lower pitchers, the inner surface of the pitchers is wholly glandular.
Wings are reduced to ribs that run down the front of the pitcher.
In aerial pitchers, the flattened peristome is up 6 mm wide and bears more prominent teeth (≤1 mm long).
The spur is usually simple and grows to 3.5 mm in length.
Compared to lower pitchers, the lid in upper pitchers is similar in shape but longer, reaching 4.8 cm in length and 0.9 cm in width.
It is held over the pitcher mouth at an angle of approximately 45 degrees.

Nepenthes jamban has a racemose inflorescence.
In male plants, the inflorescence may be up to 18 cm long.
The female inflorescence has not been described.
The rachis is up to 11.5 cm long, while the peduncle is up to 6.5 cm long.
Pedicels are up to 1.4 cm long and bear a single flower.
Sepals are elliptical and around 3.5 mm long.
Mature fruits are up to 3 cm long and 6 mm wide.
Seeds are filiform and around 2 cm long.

Most parts of the plant are glabrous.
Developing pitchers, tendrils, and inflorescences are densely covered with short brownish-grey hairs.

The stem is characteristically purplish red.
The leaves and inflorescence are light green to pale green.
Lower pitchers range in colour from yellowish orange to bright red throughout.
Upper pitchers are generally bright yellow with a yellow to orange peristome, and may be occasionally speckled on their inner surfaces.
Nepenthes jamban is a climbing plant. The stem, which is usually less than 5 mm thick, grows to 4 m in length and is cylindrical-angular in cross section. Internodes are up to 5 cm long.
Leaves are sessile and coriaceous in texture. The lamina may be narrowly obovate to elliptic or slightly spathulate, and grows to 11 cm in length and 3.3 cm in width. One or two longitudinal veins are present on either side of the midrib together with numerous pinnate veins. Tendrils are up to 24 cm long.
Rosette and lower pitchers are cylindrical to narrowly infundibular in the lower
third, becoming widely infundibular above. They are relatively small, rarely exceeding 5.8 cm in height and 4.4 cm in width. Fringed wings (≤2 mm wide) are usually present in terrestrial pitchers. The pitcher mouth is almost horizontal. The inner surface of the pitchers is glandular throughout. The flattened peristome may be up to 8 mm wide and is lined with a series of teeth (≤0.5 mm long) on its inner margin. The lid or operculum is narrowly obovate, and up to 3.8 cm long and 1.3 cm wide. The undersurface of the lid bears scattered small red glands that are concentrated around the midrib. Around 20 to 30 very large crater-like glands (≤0.5 mm wide) are present in the apical quarter. These glands are so large that they are visible as swellings on the upper surface of the lid. The spur (≤4 mm long) is inserted at the base of the lid. It is generally unbranched but may be forked.
Upper pitchers are circular in cross section and widely infundibular in their upper half. They are much larger than lower pitchers, reaching 12 cm in height and 5.2 cm in width. The pitcher mouth is horizontal and orbicular. As in lower pitchers, the inner surface of the pitchers is wholly glandular. Wings are reduced to ribs that run down the front of the pitcher. In aerial pitchers, the flattened peristome is up 6 mm wide and bears more prominent teeth (≤1 mm long). The spur is usually simple and grows to 3.5 mm in length. Compared to lower pitchers, the lid in upper pitchers is similar in shape but longer, reaching 4.8 cm in length and 0.9 cm in width. It is held over the pitcher mouth at an angle of approximately 45 degrees.
Nepenthes jamban has a racemose inflorescence. In male plants, the inflorescence may be up to 18 cm long. The female inflorescence has not been described. The rachis is up to 11.5 cm long, while the peduncle is up to 6.5 cm long. Pedicels are up to 1.4 cm long and bear a single flower. Sepals are elliptical and around 3.5 mm long. Mature fruits are up to 3 cm long and 6 mm wide. Seeds are filiform and around 2 cm long.
Most parts of the plant are glabrous. Developing pitchers, tendrils, and inflorescences are densely covered with short brownish-grey hairs.
The stem is characteristically purplish red. The leaves and inflorescence are light green to pale green. Lower pitchers range in colour from yellowish orange to bright red throughout. Upper pitchers are generally bright yellow with a yellow to orange peristome, and may be occasionally speckled on their inner surfaces.
Nepenthes jamban