The cross-linked pentapeptides (2R, 7R)-diaminooctanedioyl- bis(Tyr-Arg-Leu-Arg-Tyr-amide) ((2R, 7R)BVD- 74D, (2R, 7R)-1) and octanedioyl-bis(Tyr-Arg-Leu-ArgTyr- amide) (2) as well as the pentapeptide Ac-Tyr-Arg-LeuArg- Tyr-amide (3) were previously described as neuropeptide Y Y-4 receptor (Y4R) partial agonists. Here, we report on a series of analogues of (2R, 7R)-1 and 2 in which Arg(2), Leu(3), or Arg(4) were replaced by the respective aza-amino acids. The replacement of Arg(2) in 3 with a carbamoylated arginine building block and the extension of the N-terminus by an additional arginine led to the high-affinity hexapeptide Ac-Arg-Tyr-N-omega-[(4-aminobutyl) aminocarbonyl] Arg-Leu-Arg-Tyr-amide (35), which was used as a precursor for a D-amino acid scan. The target compounds were investigated for Y4R functional activity in assays with complementary readouts: aequorin Ca2+ and beta-arrestin 1 or beta-arrestin 2 assays. In contrast to the parent compounds, which are Y4R agonists, several ligands were able to suppress the effect elicited by the endogenous ligand pancreatic polypeptide and therefore represent a novel class of peptide Y4R antagonists.