© 2018, Springer-Verlag GmbH Austria, part of Springer Nature.The time independent Dirac equation is solved analytically for equal scalar and vector hyperbolic potential function in the presence of Greene and Aldrich approximation scheme. The bound state energy equation and spinor wave functions expressed by the hypergeometric function have been obtained in detail with asymptotic iteration approach. In order to indicate the accuracy of this different approach proposed to solve second order linear differential equations, we present that in the non-relativistic limit, analytical solutions of the Dirac equation converge to those of the Schrödinger one. We introduce numerical results of the theoretical analysis for hyperbolic potential function. Bound states corresponding to arbitrary values of n and l are reported for potential parameters covering a wide range of interaction. Also, we investigate relativistic vibrational energy spectra of alkali metal diatomic molecules in the different electronic states. It is observed that theoretical vibrational energy values are consistent with experimental Rydberg–Klein–Rees (RKR) results and vibrational energies of NaK, K2 and KRb diatomic molecules interacting with hyperbolic potential smoothly converge to the experimental dissociation limit De= 2508 cm- 1, 254 cm- 1 and 4221 cm- 1, respectively..