In this paper, we study Sturm-Liouville differential operators with a constant delay and transmission boundary conditions. We establish properties of the spectral characteristics function in the Dirichlet and Dirichlet-Neumann boundary conditions. So, we investigate the inverse problem of recovering operators from their spectra. Also, we construct the potential function by using the Fourier series of the Sturm--Liouville differential operator. The efficiency of the present method are demonstrated through several examples.