Otholobium saxosum is a small shrublet of up to 20 cm (7.9 in) high that has been assigned to the Pea family, with branches upright or horizontal at the base with rising tips.

[1] Otholobium saxosum is a small shrublet of up to 20 cm (7.9 in) high, with branches upright or horizontal at the base with rising tips.

The tip of the leaflets is pointy or blunt, but the middle vein always extends from the leaf blade into a straight point.

Each triplet of flowers sit on a inflorescence stalk and is subtended by an inverted lanceolate to fan-shaped bract of 3–3.5 mm (0.12–0.14 in) long with many veins.

The keel envelops a hollow, open tube of 5–5.5 mm (0.20–0.22 in) long, made up of nine merged filaments and one free stamen.

At the tip, the ovary extends into a hairless style that strongly widens at the place where it curves upwards about 1.5 mm from its end.

[1] Otholobium saxosum differs from O. polyphyllum, which is a taller, bushy, upright shrub (not a small, more or less upright or ascending shrublet), with obliquely oblong leaflets (not inverted egg-shaped), pointy oval stipules (not awl-shaped), flowers of 6–7 mm long with an oval standard (not 9–10 mm with an elliptic standard), calyx teeth next to the standard that are fused over two-thirds of their length (not fused for only 1 mm) and an oblong bract subtending each triplet of flowers (not narrowly lance-shaped).

O. bowieanum is the only other species in this genus with white flowers, stalkless, clover-like leaves and asymmetrical side leaflets that also grows on Garcia's Pass and the adjacent mountains.

Charles Stirton and A. Muthama Muasya considered it sufficiently different from its relatives, described it in 2017, and called it Otholobium saxosum.