This paper presents a nonlinear observer design method for acceleration control of tail-controlled Skid-to-Turn missiles. A nonlinear observer for wind angles (angle of attack and sideslip angle) is designed using a parametric affine missile model developed by the authors. Using the estimated wind angles, a desired acceleration tracking performance can be obtained by a nonlinear control based on a parametric affine missile model. The performance and stability of the proposed observer are analyzed. Simulation results are also included to show that the proposed approach can give a satisfactory performance for missile dynamics.