A two-stage autocorrelation approach is proposed for single-tone frequency estimation of a real sinusoid in white noise. In the first stage, we transform the received data to another noisy sinusoidal sequence of same frequency via an autocorrelation procedure. Autocorrelation functions of the converted sequence are then employed for frequency estimation in the second stage. A simple frequency estimator is first derived, followed by a generalized algorithm. Computer simulations are included to illustrate the accuracy of our proposed approach via comparison with Crame