There were a number of 24 teams took part in the Ranji Trophy, 1965-66 and the teams were coming from all over India. The BCCI officials divided the teams into five different zones, according to the rules and regulations of the tournament and the teams competed with each other for the ultimate aim of winning the trophy. The teams that took part in the tournament included the likes of Andhra, Assam, Baroda, Bengal, Bihar, Bombay, Delhi, Gujarat, Hyderabad, Jammu & Kashmir, Kerala, Maharashtra, Madhya Pradesh, Madras, Mysore, Northern Punjab, Orissa, Railways, Rajasthan, Saurashtra, Southern Punjab, Services, Uttar Pradesh and the Vidarbha.

Ranji Trophy, 1965-66 Central Zone League Matches: The participating teams in the Central Zone of the Ranji Trophy, 1965-66 were the likes of Madhya Pradesh, Rajasthan, Vidarbha and Uttar Pradesh and all of them were from the Central India. The teams played against each other for becoming one of the top two teams of the zone and also for securing a birth in the knock out level of the tournament. However, only the teams like Rajasthan and Uttar Pradesh could do so and were promoted to the knock out level.

Ranji Trophy, 1965-66 East Zone League Matches: All the four teams that have been playing in the previous editions of the Ranji Trophy under the East Zone, did play in the same zone in the Ranji Trophy, 1965-66. The teams were the likes of Assam, Bengal, Bihar and Orissa and coming from the Eastern region of India, all of them played against each other for entering into the knock out level. The toppers of the East Zone in the Ranji Trophy, 1965-66 were the teams like Bengal and Bihar and they competed with the top teams of the other zones in the knock out level of the tournament.

Ranji Trophy, 1965-66 North Zone League Matches: The North Zone in the Ranji Trophy, 1965-66 saw the participation of a number of 6 teams, all from the Northern part of India. There was no change in the participating teams, as the teams that were participating in the previous editions, participated in the Ranji Trophy, 1965-66, as well. The teams included the likes of Northern Punjab, Southern Punjab, Delhi, Jammu & Kashmir, Services and Railways and all of them vied for a birth in the knock out level of the tournament. The teams like Delhi and Services eventually represented the North Zone in the knock out level.

Ranji Trophy, 1965-66 South Zone League Matches: There were a number of 5 teams that competed with each other under the South Zone of the Ranji Trophy, 1965-66 and the teams included the likes of Hyderabad, Kerala, Andhra, Mysore and Madras. The teams played against each other in the zonal league matches first and they tried their best to become one of the top two teams of the zone. They also competed against each other for securing a birth in the knock out level of the tournament, however, only the teams of Mysore and Hyderabad could do so from the South Zone.

Ranji Trophy, 1965-66 West Zone League Matches: The West Zone of the Ranji Trophy, 1965-66 saw the participation from a number of 5 teams, all coming from the Western region of India. The teams that took part in the tournament under the West Zone included the likes of Maharashtra, Bombay, Baroda, Gujarat and Saurashtra. Though all the teams tried their best to get a chance into the knock out level of the tournament, only the teams like Bombay and Maharashtra became successful to do so from the West Zone. They went on to compete with the top teams of the other zones in the knock out level of the tournament.

Ranji Trophy, 1965-66 Knock out Matches: The knock out matches in the Ranji Trophy, 1965-65 saw a tough battle between the top teams of the five zones, all vying for the championship trophy. There were a number of five teams that played in the knock out level of the tournament and the teams included the likes of Rajasthan, Services, Bombay, Bengal and Mysore. However, there was no change in the ultimate result of the tournament, as the Bombay team continued to dominate all the other teams in the tournament and won the trophy, yet again.