Dillwynia tenuifolia is an erect shrub that typically grows to a height of, its stems covered with shortcurved hairs. The leaves are linear, glabrous or sometimes hairy near the tip, and long. The flowers are usually arranged singly in leaf axils or on the ends of branchlets on a peduncle less than long. There are bracts and bracteoles about long. The sepals are long and the standard petal is orange-yellow and red, long. Flowering mainly occurs from February to March and the fruit is a pod long.