In this paper, we propose a decentralized control system of multiple mobile manipulators handling a single object in coordination without using force/torque sensors. In this system, the grasping point of each robot is controlled as if it has an impedance dynamics without using a force/torque sensor, by using the identified parameters of each robot. These robots handle a single object in coordination using a leader-follower type control algorithm. We also consider the effect of parameter identification errors and propose a method to reduce the effect of them. The proposed control system is experimentally applied to two mobile manipulators, and the experimental results illustrate the validity of the proposed control system.