As75 NMR measurements were performed on a polycrystalline sample of spin-12 alternating spin chain Heisenberg antiferromagnet AgVOAsO4. The temperature-dependent NMR shift K(T), which is a direct measure of the intrinsic spin susceptibility, agrees very well with the spin-12 alternating-chain model, justifying the assignment of the spin lattice. From the analysis of K(T), magnetic exchange parameters were estimated as follows: the leading exchange J/kB≃38.4 K and the alternation ratio α=J′/J≃0.69. The transferred hyperfine coupling between the As75 nucleus and V4+ spins obtained by comparing the NMR shift with the bulk susceptibility amounts to Ahf≃3.3TμB. The effect of interchain couplings on the low-temperature activated behavior of K(T) and the spin-lattice relaxation rate 1/T1 is identified. © 2017 American Physical Society.