A detailed study on synthesis and optical, magnetic, dielectric, and photocatalytic properties of Multiferroic co-doped Bi1−xSmxFe1−xNixO3 (x = 0.00, 0.02, 0.04, 0.06 and 0.08) (BSFNO) nanoparticles that have been prepared by tartaric acid-based sol–gel technique has been conducted. X-ray diffraction data show that high crystallite could be provided by the sharp peak and mergers of the doublet peaks, for instance (104) and (110), and (006) and (202), which indicates structural transition and XRD pattern shift towards higher angle, indicating structural distortion due to Sm and Ni co-doped BiFeO3. Raman spectroscopy also gives the confirmation of structural distortion and distorted rhombohedral perovskite structure with R3c symmetry. FESEM studies have revealed microstructural and nanocrystalline nature of BSFNO, a nanostructured material, and elemental analysis was done by EDX. The particle size of BSFNO (x = 0.02, 0.04) was analyzed by TEM and the average size of the particle was found to be ~ 50 nm. The identification of elements, chemical shift, oxidation state of elements ,and oxygen vacancies of the Sm and Ni co-doped BiFeO3 (x = 0.02 and 0.06) samples were analyzed by XPS. The calculated energy band gap values for BSFNO, a nanostructured material, were found to be 2.3 eV, 2.03 eV, 2.04 eV, 2.03 eV, 2.04 eV, respectively (from UV–VIS spectra). These results provide preliminary research for optoelectronic device and infrared detector. An enhancement in saturation magnetization has been observed with the substitution of Sm and Ni co-doped in BFO. Similarly enhancement in the dielectric constant (e) and dielectric loss (tanδ) has been observed with the substitution of Sm and Ni co-doping in BFO. The photocatalytic properties enhanced in co-doped BSFNO in comparison to pure BFO. The % efficiency and degradation of co-doped BSFNO increases when compared to pure BFO.