Y 3 Fe 5 O 12 thin films with thickness 10 nm ≤ t ≤ 1440 nm were grown on Gd 3 Ga 5 O 12 (111) substrates by pulsed laser deposition. The X-ray diffraction experiments confirmed the films are pure yttrium iron garnet (YIG) phase with preferred (111) orientation. The magnetic and microwave properties were studied as a function of film thickness by the dc magnetization and ferromagnetic resonance (FMR) measurements. The FMR linewidth (ΔH) was found to decrease with the increase in film thickness (10 nm ≤ t ≤ 45 nm), attaining a minimum value of ΔH ⊥ = 5 Oe and ΔH || = 6 Oe, for perpendicular and parallel resonance, and then rising with further increase in thickness. Acid etching experiments were performed to understand the mechanism contributing to ΔH. The increase in ΔH with thickness (t > 45 nm) may be explained in terms of extrinsic mechanisms, such as inhomogeneities present at the surface of the films. However, the decrease in ΔH with thickness (t <; 45 nm) is believed to be due to the surface anisotropy effect. The films showed low coercivity values in the range of ~1.5-7 Oe, which is an indicator of good quality YIG films.