Phacelia cookei is a rare species of phacelia known by the common name Cooke's phacelia. It is endemic to Siskiyou County, California, where it is known from just a few occurrences in the forest and scrub around Mount Shasta. The substrate in the area is sandy, ashy volcanic soil. It is an annual herb growing in a small, flat mat or with a short upright stem a few centimeters high. It is blue-green in color, succulent, and lightly hairy. The oval, smooth-edged leaves are one or two centimeters long and borne on short petioles. The hairy inflorescence is a one-sided curving or coiling cyme of several tiny bell-shaped flowers. Each flower is white with lavender veining, about half a millimeter wide and no more than 2 millimeters long.