A silver metal and epoxy device 1 3/16 inches (3.02 cm) in height, blazoned as follows: Per chevron reversed Argent and Vert a pitchfork erect throughout, points to chief, surmounted in base by an open book bound Gules leaved Proper bearing a quill pen bend sinisterwise between the Roman letters Mt and D Argent (Silver). Above the shield a red scroll inscribed, MT DIABLO HS in silver letters and arching below the shield, a tri-parted red scroll inscribed, VICTORY WITH HONOR in silver letters.

Crimson and Green are the school colors. The shield division of the chevron represents the peaks of Mount Diablo. The pitchfork harkens back to the school mascot Danny the Devil and in the erect honorable position symbolizes victory with honor. The open book with the quill stands for education and specialized programs known as the academies in which the students of Mt Diablo are enrolled.