[en] We present ²⁷Al NMR studies for a single crystal of the newly developed superconductor NpPd₅Al₂ (T_c=4.9 K). In the superconducting state, the ²⁷Al NMR spectrum shifts to lower frequencies owing to a decrease of the spin part of the Knight shift, and exhibits broadening characteristic of the local field distribution associated with a vortex lattice. We have also found that the ²⁷Al nuclear spin-lattice relaxation rate (1/T₁) decreases just below T_c with no coherence peak and shows T³ behavior at low temperatures. The observed temperature dependences of the Knight shift and 1/T₁ in general accord with those assuming a line-node superconducting gap with the gap value of 2Δ/k_BT_c≅6.4. Therefore, the present NMR data provides evidence for strong-coupling d-wave superconductivity in NpPd₅Al₂. (author)