The Glottal Closure and Opening instants (GCIs and GOIs) form important events in excitation source signal. These instants represent closing and opening events of vocal folds while producing voiced speech signal. Estimation of such instants from speech signal is beneficial and several applications rely on accurate estimation of Closure and Opening instants. In this work, Electroglottographic like (EGG-like) signal is synthesized from speech signal using Generative Adversarial Network (GAN). The Glottal Closure and Opening instants are located using the derivative of EGG-like signal, which is essentially a difference EGG-like signal. The proposed method is evaluated on CMU-Arctic database, as the database consists of simultaneous recordings of speech and EGG signal, respectively. To evaluate the results, the locations obtained from synthesized EGG-like signal are com-pared with the reference difference EGG signal. The results are evaluated for both seen and unseen conditions. It is shown that the performance of GCI and GOI estimation is comparable to existing state-of-the-art methods. © 2019 IEEE.