Temperature-dependent zero-, longitudinal- and transverse-field μSR spectra have been recorded in nanometric Fe13Cu10Ag77 obtained by mechanical alloying. The alloy comprises Fe(Cu) nanoparticles (5nm) in a Ag matrix formed by 16nm particles, as deduced from the Rietveld refinement of the X-ray diffraction pattern. The muon depolarization can be described by a Dynamical Lorentzian Kubo–Toyabe function. This is in agreement with a high degree of interparticle dipolar interactions, giving rise to a cluster spin glass-like behavior below 100K. The intra particle interactions are also probed by the μSR, and influence the thermal variation of the static width.