Second harmonic generation from the spin coated films of an asymmetrically substituted polydiacetylene, namely poly ((8-butoxy carbonyl) Methyl urethanyl) l- (5-pyrimidyl) -octa-l,3-diyne (BPOD) is reported for the first time. The Macromolecules assemble to produce the organization responsible for SHG without recourse to poling. d33 of the spin coated film (0.19–0.31 μm thickness) are between 0.78–0.88 pm/V without absorption correction and 3.32–5.57 pm/V after correction. Angular and polarization dependence study of the second harmonic response suggests that the film has in-plane isotropy as a whole and the net dipole is nearly perpendicular to the film surface. Spontaneous orientation of the polymer chains during the film formation seems to be responsible for the noncentrosymmetric alignment of the polymer. SHG from the Langmuir Blodgett films are also reported.