The Jamnagar district, originally constituted as Halar district, is not only recent in its origin but also in its modern set up. But the region comprised therein is of great antiquity and dates back to ancient periods of Jamnagar. According to Pauranik literature, Lord Krishna established his kingdom at Dwarka, now in Jamnagar district, after his migration from Mathura and it is to this great Yadava race that the Jams of Nawanagar trace their descent.

The foundation of Nawanagar State is credited to Jam Raval. In AD 1540 after winning conquests Jam Raval founded the city of Nawanagar.

During the rule of His Highness Jam Ranjitsinhji, between 1920 - 1930, he developed the city according to western architecture and built Power House, Vibha Vilas Palace, Jam Bunglow (Bhavendra Vilas Palace), Pratap Vilas Palace, Mann Vilas, Amar Vilas, Arch Vilas, Badminton House, Filtzer House, Coach House, Irwin Hospital, Solarium, Vegetable Market, Grain Market, Nana-Ashapura's Temple, Sajuba Girls' High School, Wellington Crescent, Bedi Bunder, Rajput Boarding, Infantry Lines, Jam Raval's Statue, Jam Ranjit's Statue, Nursing School, Dayaram Library, Port Office, Central Bank, Summair Club, Railway Station, Parsi Agiyari, Anandabava Ashram, extention of Lal Bunglow, Ranjit Road, Central Bank Road, Rajendra Road, Khambhalia Gate Road, Jam Bunglow Road, Talav-ni-Pal Road, being the main ones.

After His Highness Jam Ranjitsinhji, His Highness Digvijaysinhji was bethroned (1933 - 1948) and he built Digvijay Woollen Mills, Aerodrome, Dhanvantri Mandir, Digvijay Plot, Gulabnagar, Valsura, Ranjit Swimming Pool.

The present district takes its name from the city and capital of Jamnagar so named after the rulers who styled themselves as Jams.

The Halar district which was constituted for the first time in the year 1949 after the merger of princely states into the state of Saurashtra, constituted of the former Indian states of Nawanagar and Dhrol, Dhrafa Thana and part of Jalia Dewani. After re-organization several territorial changes were effected in practically all the districts of Saurashtra. On June 19th 1959, the boundaries of the district got enlarged by the inclusion of the adjoining Okhamandal, when Halar district was renamed Jamnagar. This district became part of the newly born State of Gujarat on the bifurcation of the composite State of Bombay on May 1st 1960.In the year 1961 the district consisted of 720 villages and 15 towns.