The Knight shift of the Al27 NMR in SmAl3 has been measured in the temperature region from 78 to 400°K, and the susceptibility of SmAl3 has been measured up to 850°K. The part of the Knight shift arising from polarization of the conduction electrons through exchange with the 4f electrons reverses sign at (310+/-20) °K, and the relation between the Knight shift and the susceptibility is not linear. This behavior results mainly from Van Vleck-type paramagnetism, and could adequately be calculated on the basis of free Sm3+ ions. The parameters used are the multiplet splitting constant Ak=(410+/-20)°K, and the interionic exchange constant Iffk=-(15+/-5)°K, indicating antiferromagnetic ordering at low temperatures. The effective exchange constant between the conduction-electron spins and the 4f-electron spins has been found to be Isf=-0.21 eV, equalling those derived for other RAl3 compounds (R=rare earth). The nuclear quadrupole coupling has been measured to be |e2qQ|h=(0.8+/-0.1) Mc/sec, and is discussed in terms of the point-charge model.