Defects in the bearings greatly affect vibrations and performances of rotating transmission systems. Moreover, most previous works estimated the defect shape as a regular shape. However, the actual defect shape is not actually regular. To obtain more accurate vibration characteristics of a defective double row cylindrical roller bearing, an irregular-shaped defect modeling method and a dynamic model of double row cylindrical roller bearing with irregular-shaped defects are proposed in this paper. The dynamic model includes all components and their interactions. A test verification is proposed to validate the established model. The effects of the bearing load, rotating speed, and different independent shape defect sizes on the double row cylindrical roller bearing vibrations are investigated. The comparisons of vibrations between the irregular defect shape and simplified defect shape are studied. The results show that the simplified defect shape model will cause the vibrations to be overestimated. The established dynamic model with the actual defect is more reasonable than the simplified defect model. Moreover, this paper can provide a comprehensive analytical method for double row cylindrical roller bearing vibrations.