In this paper, we tackle the position tracking problem in a robotic tele-operation setup in the presence of perturbations. In order to cope with the disturbance we developed a new disturbance observer. The estimation algorithm uses only position and velocity information and we study the estimation error dynamics in the face of constant and nonconstant exogenous perturbation signals. The disturbance estimator is used in a trajectory tracking controller to improve the performance of the position tracking between the master and the slave robot. The algorithm is tested in simulation on a tele-operation system with two two-link robots.