The structural, microstructural, and surface morphological properties of Ba0.5Sr0.5TiO3 thin films were investigated as a function of Ni dopant concentration. The Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties as well as film growth rate, Ni doped (less than or equal to3 mol%) BST films showed denser, smoother, and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 980 and 0.3%,. respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. Correlation of the material properties with dielectric and tunable properties suggests the the 3 mol% Ni-doped BST films are the optimal choice for tunable device applications.