Regular and irregular dislocation networks have been observed under a transmission electron microscope (TEM) in melt-textured Bi1.85V0.15Sr2Ca2Cu3Oy superconductors. From our previous experience in TEM observation, such dislocation networks cannot be found in polycrystalline and melt-textured Bi2Sr2Ca2Cu3Oy superconductors. We believe that these planar defects arise from the substitution of vanadium atoms, rendering a stronger bonding between the V and O atoms. The networks are conjectured to be possible planar pinning centres for magnetic flux in the superconducting state.