Electrical transport properties of RNiO3 (R = Pr, Nd, Sm) thin films grown by pulsed laser deposition have been studied. RNiO3 films grow in the (100) direction on a LaAlO3 (100) substrate. Unlike the polycrystalline solid, PrNiO3 films showed metallic behavior. The first-order metal-to-insulator transition observed in polycrystalline solids is suppressed in RNiO3 films. The effect of lattice strain in the films influencing the transport properties has been studied by varying the thickness of PrNiO3 film on LaAlO3 (100) and also by growing them on SrTiO3 (100) and alpha-Al2O3 (1 (1) over bar 02) substrates. Deviation in the transport properties is explained due to the strain-induced growth of the films. Further, we show that the transport property of a LaNiO3 film is also influenced by a similar strain effect.