An elongated generally rectangular ceiling plank formed of wood or plastic composition and has opposite elongated side edges with a length that is between nine and ten times the width of the opposite end edges. The ceiling plank includes complementary tongue and groove engagement portions formed at the sides and ends for side-by-side or end-to-end engagement with other similar planks. In a ceiling plank installation a ceiling plank securement clip secures the side groove portion of one plank to a ceiling. The secured plank can be joined to another plank in side-by-side or end-to-end engagement at a ceiling by interengagement with the tongue portion at the side or end of the other plank. The ceiling plank is approximately forty-eight inches long and five inches wide and can thus be easily handled and installed by one person.