Microstructures of Barium Strontium Titanate (Ba, Sr)TiO3 [BST] thin film play an important role in determining the electrical properties of BST. In particular, it is found that the grain size distribution as a function of deposition conditions correlates with the dielectric constant of BST film. Traditionally, Transmission Electron Microscopy (TEM) provides an accurate method for determining microstructures such as interface structure between BST and electrodes and BST grain size distribution. However, TEM analysis relies heavily upon successful sample preparation, and film adhesion for BST proves to be a difficult problem to overcome for successful sample preparation. With the state of the art Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM), useful information can be obtained for BST and electrode microstructures requiring little or no sample preparation. A good correlation among TEM, SEM and AFM techniques is achieved which allows useful information of BST grain size distribution to he obtained via SEM and AFM analyses. Power spectral density (PSD) analysis of contrast enhanced AFM images proves to be an efficient method for estimating BST grain size distribution.