The solid solution (1-x)Pb(Ni1/3 Nb2/3)O3-xPbTiO3 (PNN-PT) exhibits relaxor to purely ferroelectric behaviour with large piezoelectric coefficients near the so-called Morphotropic Phase Boundary (MPB) by increasing the PT amount. This is for example the case for many other relaxor-PT systems like PMN-PT, PZN-PT, ... Here, the presence of Ni cations enriches this solid solution by providing potential magnetic and optical features making PNN-PT a multifunctional perovskite oxide. Therefore the structural, electronic, dielectric, piezoelectric, optical and magnetic properties were systematically investigated on a broad range of compositions, ranging from x=0 to x=0.6. We show indeed strong relaxor-like properties (dielectric relaxation, electrostriction) and large piezoelectric coefficient reaching 1000 pC/N at room temperature near the MPB at x=0.35. The optical properties (reflectance, band gap, ...) reveal the absorbance potentialities of PNN-PT in the visible and UV range. In addition, the study of the lattice constant with temperature, coupled to calorimetric experiments, point to a possible Jahn-Teller distortion related to low to high spin transition of the Nickel ion near room temperature for solid solution with low PT content