Phacelia rattanii is an annual herb growing 15 centimeters to one meter in maximum stem length, taking an erect, branching form. It is glandular and coated in stiff hairs and bristles with bulbous bases. The leaves are oval, toothed or lobed, and up to about 7 centimeters long. The hairy inflorescence is a one-sided curving or coiling cyme of bell-shaped flowers each no more than half a centimeter long. The flowers are white to light blue and are surrounded by calyces of sepals coated in long hairs.
