A mass and center of mass location estimation strategy for a multi-lift slung load is proposed is this paper. Motion of the slung load is analyzed to build the relation between cable force and payload response. Here, cable force is computed using an indirect method without attaching any tension load sensor. An estimator based on slung load response to cable forces is used to estimate mass and the position of the center of mass. Three different estimators (least squares, maximum likelihood, and Kalman filter) are derived and compared for this estimation problem. Flight tests performed indoor in a Vicon motion capture studio validate the proposed method. The payload mass can be estimated with an error less than 7%. To verify estimation of center of mass, extra weight is added to the payload. Results show the estimated change of center of mass is within a few millimeters of truth, with convergence requiring less than ten seconds.