We have performed 27 Al and 55 Mn nuclear magnetic resonance (NMR) measurements on a single crystal of YMn 4 Al 3 at 8T. 27 Al NMR spectrum shows two sets of satellites from two different Al sites. Based on the difference in NMR shift, linewidth and relaxation rates, two sets of NMR resonance peaks were assigned to the respective Al sites. NMR shift and spin–lattice and transverse relaxation rates, 1/T1 and 1/T2, were measured down to 4 K at 8T. Shift and linewidth for 27 Al and 55 Mn NMR follow temperature dependence of the susceptibility, confirming that the hyperfine field from Mn 3d spins dominates local electronic structures at both Al and Mn sites.