Here we demonstrate that peptidic inhibitors can be designed based on the α-helical CBM domain of the DmBam protein which binds the NOT9 subunit. The 22 amino acid long NIP-WT was truncated to a 17-residue peptide and subsequently, a panel of hydrocarbon-stapled peptides was designed to improve affinity and permeability. Among the different stapled peptides, NIP-2 exhibited the highest binding affinity based on the FP experiments, which correlated with high α-helicity as measured by CD spectral analysis. As expected, NIP-2 was able to compete with RNA for binding to NOT9 which is an essential requirement for the inhibition of the deadenylation process and confirms the overlap between the protein and RNA binding sites on NOT9. Furthermore, NIP-2 was able to inhibit deadenylation of a model RNA by the minimal CCR4-NOTcore complex. These results confirm that NOT9 enhances deadenylation rates by inducing proximity between the target RNA and the active deadenylases. When inhibition of deadenylation was tested using lysates that contain the full CCR4-NOT complex we found that NIP-2 did not fully inhibit poly(A) tail removal of the model RNA even at micromolar concentrations. The residual deadenylation activity potentially indicates that various other subunits are involved in non-specific RNA recruitment to the CCR4-NOT complex or it is an indication of PAN2-PAN3 complex activity.