Wat Phra Si Mahathat is home to a significant relic, the Phra Chedi Si Mahathat. Inside, there is a smaller chedi enshrining the sacred relics, and the walls feature niches containing the ashes of individuals who have contributed to the nation, as recognized by the government and the House of Representatives. Additionally, there is the Phra Si Sampuddhamunee, the main Buddha statue in the ubosot, representing the Sukhothai style of the Buddha in the Mara Victory posture, which was originally placed in front of the palace.