In this study, we explored the structural dynamics of Mcl-1, an anti-apoptotic protein. On the basis of structural ensembles, the essential dynamics was extracted and showed two major axes of variability: a breathing motion at the binding interface and a correlated motion through the internal loops. A free energy surface characterizing the breathing motion at the binding interface was generated and suggested an equilibrium between a closed conformation and a "ready to bind" conformation as the predominant states of Mcl-1 in solution. Moreover, the analysis of the dynamics along the internal loops revealed a hidden communication network of transient and cryptic pockets controlling the allosteric inhibition of Mcl-1. A detailed model joining the pocket crosstalk and salt bridge networks along the internal loops was proposed and allowed us to shed light on the key interactions governing Mcl-1's allosteric inhibition.