We present the detailed optical evolution of a Type Ib SN 2015dj in NGC 7371, using data spanning up to similar to 170 days after discovery. SN 2015dj shares similarity in light-curve shape with SN 2007gr and peaks at M-V = -17.37 +/- 0.02 mag. Analytical modeling of the quasi bolometric light curve yields 0.06 +/- 0.01 M-circle dot of Ni-56, ejecta mass = M-ej = 1.4(-0.5)(+1.3) M-circle dot, and kinetic energy E-k = 0.7(-0.3)(+0.6) x 10(51) erg. The spectral features show a fast evolution and resemble those of spherically symmetric ejecta. The analysis of nebular phase spectral lines indicates a progenitor mass between 13-20 M-circle dot, suggesting a binary scenario.