Thin films of (Y1−xEux)Ba2Cu3O7−δ with x = 0–1 were grown by pulsed laser deposition on single crystal substrates, todetermine the effect of Y and Eu substitution on the microstructuraland superconducting properties. The film critical transition temperature(Tc), criticalcurrent density (Jc) and surface roughness were found to be strongly dependenton the substrate choice, with the best properties achieved onCeO2–YSZ substrates. Substrates with varying lattice mismatch from−2% to+1% were studied,including LaAlO3, SrTiO3,CeO2-buffer-coatedZr0.905Y0.095O2 (YSZ),and (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT). With increasing Eu substitution fromx = 0 to1, the Tc on CeO2–YSZ substrates increased steadily from 89 to 93 K. The value ofJc was measured by magnetic methods at 65 and 77 K, and by transportmethods at 77 K for selected samples and different angles of orientationHappl(θ) = 0°–90°. As Eu substitutionwas increased from x = 0 to ≥ 0.2, Jc at 77 K increased strongly more than two-fold for T and for H<0.5 T forall orientations 0°≤θ≤90°; but, it decreased more than two-fold for T. The Jc(H) properties at both low and high fields correlated well with microstructural featuresobserved by scanning electron microscopy. The low-field was enhanced when the grain size was reduced to∼100 nm size, and theself-field and high-field Jc(H) appeared to be strongly affected by the film density and porosity. A controlled dense-island structure wasnoted for x = 0.75, on CeO2–YSZ substrate.