Multiple systemic risk factors are associated with retinopathy of prematurity (ROP). We analyzed the role of low weight gain (WG) to predict the development of stage 3+ ROP among preterm infants. This study included 126 newborns with birth weight ≤1500 g and gestational age <32 weeks. Preterm newborn infants were divided into two groups according to severity of ROP as: preterm infants without ROP or mild ROP (Group 1) and preterm infants with stage 3+ ROP (Group 2). WG and WG proportion were measured at completed 4 and 6 weeks of life. The patients under the cut-off point according to receiver operating characteristic curve were classified as low WG patients. WG and WG proportion were significantly lower in Group 2 than in Group 1 at the 4th and 6th weeks of life. We concluded that low WG and WG proportion at the 4th and 6th weeks of life were predictive for the development of stage 3+ ROP. Preterm babies with low birth weight and low WG should be followed closely for severe ROP.