27Al and 31P nuclear magnetic resonance (NMR) spectroscopies were used to investigate aluminum interactions at pH 3.4 with model membranes composed of 1-palmitoyl 2-oleoyl-sn-glycero-3-phosphocholine (POPC). A solution state 27Al NMR difference assay was developed to quantify aluminum binding to POPC multilamellar vesicles (MLVs). Corresponding one-dimensional (1D) fast magic angle spinning (MAS) 31P NMR spectra showed that aluminum induced the appearance of two new isotropic resonances for POPC shifted to −6.4 ppm and −9.6 ppm upfield relative to, and in slow exchange with, the control resonance at −0.6 ppm. Correlation of the 27Al and 31P NMR binding data revealed a 1:2 aluminum:phospholipid stoichiometry in the aluminum-bound complex at −9.6 ppm and a 1:1 aluminum:phospholipid stoichiometry in that at −6.4 ppm. Slow MAS 31P NMR spectra demonstrated shifts in the anisotropic chemical shift tensor components of the aluminum-bound POPC consistent with a close coordination of aluminum with phosphorus. A model of the aluminum-bis-phospholipid complex is proposed on the basis of these findings.