Neurotensin (NT) is a 13 amino acid peptide expressed in the central nervous, gastro-intestinal and cardiovascular systems where it acts as a neuromodulator of classical neurotransmitters such as dopamine and glutamate, primarily through activation of neurotensin receptor 1 (NTS1), a G Protein-Coupled Receptor (GPCR). Peptide ligands of GPCRs bind through complex, and possibly multiple modes for which there are few representative crystal structures. In the case of NTS1, eight inactive-state crystal structures of thermostabilized variants have been solved in complex with the high affinity 8-13 fragment of NT (NT8-13, RRPYIL). In all crystal structures, NT8-13 adopts an identical extended conformation with the C-terminal four residues (PYIL) buried deeply into the orthosteric site of the receptor. But the role of ligand conformational dynamics while bound to the orthosteric site is unclear. We used competition saturation transfer difference (STD) NMR to investigate the binding pose of a low-affinity neurotensin peptide fragment (NT10-13) to a thermostabilized, signaling-competent NTS1 variant solubilized in detergent micelles. Epitope mapping of NT10-13 suggests that tyrosine 11 (Y11) binds the NTS1 orthosteric site in an alternate conformation than previously observed in crystal structures. Using molecular dynamics (MD) simulations, we, and others, showed that Y11 can adopt two conformations on NTS1 binding. Furthermore, 13C HSQC spectra of a [U-13C,15N]-NT8-13:[U-2H,12C]-NTS1 complex revealed that the Y11 sidechain indeed exists in two conformations. Two states were also observed for the free peptide but at different populations compared to the complex. Exchange rates between the two conformers are currently being measured. Taken together, our integrative approach has captured a peptide conformation not evident from crystal structures thus highlighting the importance of NT peptide dynamics for NTS1 activation.