Since the introduction of a market economy and private farming (Doi Moi in Vietnamese), agricultural cooperatives are considered to have lost a great deal of their authority, as they became service organizations for farmer members. It has also been reported that agricultural productivity in the Red River Delta rapidly increased both in terms of cropping intensity and yield by this policy, although the technological background related to the increase has not yet been analyzed. The present study, therefore, focuses on the changes in cropping patterns at the village level after Doi Moi, particularly both from the physical and technological viewpoints. The Coc Thanh Cooperative in Nam Dinh province of Vietnam, located in an area in the lowest part of the Red River Delta, was selected for the present study. The major conclusions were; 1) a wide range of new agricultural technologies, including new varieties of rice and other upland crops, new techniques for planting of rice seedlings, and small pumps for farm-level water management and winter and spring crops were introduced by the cooperative and the farmers themselves through trial and error, resulting in a diversification of the farming systems, especially expansion of the vegetable cropping area in the winter and spring seasons, and 2) the cooperative played a key role in terms of these changes in appropriate agricultural production, including spring potato production managed by the cooperative.