A precise value for the magnetic moment of the As-69 5/2(-) ground state has been obtained from nuclear magnetic resonance on oriented nuclei (NMR/ON) using the NICOLE He-3-He-4 dilution refrigerator setup at ISOLDE/CERN. The NMR/ON signal was observed by monitoring the anisotropy of the As-69 beta particles. The center frequency nu[B-ext = 0.0994(10)T] = 169.98(9) MHz corresponds to mu[As-69] = +1.6229(16)mu(N). This result differs considerably from the pi f(5/2) single-particle value obtained with g factors for a free proton but is in reasonable agreement with the value obtained with effective g factors and with values from a core polarization calculation and from calculations in the framework of the interacting boson-fermion model. Assuming a single exponential spin-lattice relaxation behavior a relaxation time T-1' = 10(25) s was observed for (AsFe)-As-69 at a temperature of about 20 mK in a magnetic field B = 0.1 T.