Identifying the environmental hazards of jackup drilling rig, which is used as an exploratory drilling and offshore service platform, yet has been under intense discussion. Risk assessment along with determining the likelihood of an event occurrence and the severity of its consequences can be a useful tool for identifying the priorities and making satisfactory managerial decisions. In this study, the environmental risks attributed to jack-ups in the offshore area of Iran around the South Pars gas field were studied, and finally a new mathematical model for the environmental risk assessment in this area was presented. Due to qualitative nature of some indefinite factors, fuzzy logic was applied in this model. Moreover, the model design was tailored to the ecological and environmental conditions of South Pars gas field, and several sources of risk were aggregated for the final environmental risk assessment of jack-up drilling rig. The results indicated that the total risk calculated for jack-up in transportation was tolerable and limited management measures were required. However, for the jack-up operation risks, the site was found to be faced with ''unacceptable risk'' or requiring extensive management measures.