Surface and interfacial fluctuations in phase separating thin film polymer blends are investigated using atomic force microscopy (AFM) and forward recoil spectrometry. The root-mean-square roughness at the surface (R-q,R-s) and the interface beneath the wetting layer (R-q,R-i) are quantified using AFM. R-q,R-s is found to scale with the initial film thickness (l(0)) during the early and intermediate stages, consistent with the morphology evolution mechanism reported earlier; however, the entire temporal evolution of R-q,R-s does not scale with l(0). A fast Fourier transform of the AFM images uncovers low (q(l)) and high (q(h)) wavenumber fluctuations at both the surface and interface. The former fluctuation is associated with capillary fluctuations, whereas the latter reflects spinodal decomposition within the film. As the minority phase in the bulk of films undergoes 2D coarsening, the high wavenumber surface and interface fluctuations follow power-law dynamics, q(h,s) similar to t(alphas) and q(h,i) similar to t(alphai), respectively. Both -alpha(s) and -alpha(i) increase with film thickness and reach an asymptotic value of about 1/3, suggesting that decreasing film thickness inhibits the growth of short wavelength fluctuations. Furthermore, -alpha(s) is systematically less than -alpha(i), suggesting that the surface fluctuations are hindered relative to interfacial ones and that the surface and internal fluctuations are not conformal.