The microstructure of YBa2Cu3O7−xfilms on (001) and (014) SrTiO3is examined by x‐ray diffraction, optical microscopy and cross‐sectional transmission electron microscopy. The growth of YBa2Cu3O7−xin as‐deposited films is extremely anisotropic resulting in plate‐like grains with (001) surfaces. These types of YBa2Cu3O7−xgrains, 90°‐misoriented from each other, are observed to grow on both (001) and (014) surfaces of single crystal SrTiO3because in cubic SrTiO3there are three equivalent ⟨100⟩ directions that the c‐direction [001] of YBa2Cu3O7−xcan align with. On (001) SrTiO3, the (001) oriented platelets become dominant over the whole film due to the anisotropic growth‐rates, while on (014) none of the three orientations dominates resulting in smaller grain size and smoother surface. The 3‐fold degenerate epitaxy of YBa2Cu3O7−xon SrTiO3results in near‐&Sgr;1 grain boundaries with two 90°‐misoriented abutting crystals. These high angle yet crystallographically special boundaries are inevitably free of extraneous phases because of their low boundary energies and therefore, they provide intact connections between YBa2Cu3O7−xgrains throughout the film. While some extraneous phases do exist in these films, they are located away from the bounaries, and hence, are not damaging to superconducting transport. The argument agrees with the high critical current density measured (2×106A/cm2) at 77 K for a YBa2Cu3O7−xfilm on (014) SrTiO3where the measured supercurrent had to pass through at least 10 such boundaries.