Systematic studies on the structural and microstructural properties as a function of the lanthanum concentration have been performed in AgNbO3-based lead-free ceramics, which were synthesized via the conventional solid-state reaction process. The structural analysis has been carried out at room temperature by the X-ray diffraction technique as well as Raman spectroscopy. A single-phase orthorhombic polycrystalline perovskite structure, without undesired phases, has been confirmed for all studied compositions. Structural distortions, which have been associated with the doping concentration, have been investigated through Rietveld refinement and Raman results. The La3+ ion concentration has also shown an important influence on the Raman spectra, showing a wavenumber shift and a dramatic change in absolute intensity of several bands with the increase of the lanthanum dopant. With a further inclusion of the doping element, a change in the local structural properties is revealed, detecting additional bands in the 90–93 cm−1 and 570−758 cm−1 ranges of Raman spectra. The microstructure is strongly influenced by the additive content, revealing a decrease in grain-size as the La-content increases.