Phetchaburi Province has a rich history dating back to prehistoric times, with archaeological remains like pottery, ancient tools, and burial sites found in areas like Tha Yang District. Influenced by successive cultures, including Dvaravati, Khmer, and early Siamese civilizations, Phetchaburi has retained its significance through the ages. During the Khmer cultural period, a square city structure with protective walls and moats was established along the Phetchaburi River, with the Khmer temple Wat Kamphaeng Laeng as a major site. Later, evidence suggests that the city became known as "Sri Chai Wachara Buri" under Khmer influence, further marked by the Prang structures showcasing Khmer Bayon art.

The name "Phetchaburi" first appeared in Sukhothai inscriptions, indicating its importance alongside other key cities. Under Ayutthaya rule, Phetchaburi served as a fortified outpost, playing a critical role in resisting attacks from Cambodia and later Burma. The province’s influence continued into the Thonburi and early Rattanakosin periods, with Phetchaburi supporting the central government in defending Thailand’s independence.

Royal interest in Phetchaburi grew during the Bangkok period, particularly under King Mongkut (Rama IV), who constructed the grand palace "Phra Nakhon Khiri" on a nearby hill. King Chulalongkorn (Rama V) further honored the province by building the "Phra Ram Ratchaniwet" palace in the city center, while King Vajiravudh (Rama VI) later established the seaside palace "Mrigadayavan" in Cha-am for health purposes.