Background and aim Retinopathy of prematurity (ROP) is the major ocular problem of preterm infants that occurs with abnormal proliferation of immature retinal vessels. Although pentoxifylline (PTX) was reported to inhibit vasculogenesis and neovascularization in experimental studies, there is no clinical data about the effects of PTX treatment on the development and severity of ROP. This clinical study aimed to investigate the possible effects of PTX on the development of ROP. Materials and methods A single-centre retrospective study was conducted including preterm infants who were hospitalised in the neonatal intensive care unit between 2015–2017 years. Infants were divided into two groups in terms of PTX administration for adjuvant therapy, as PTX and non-PTX groups. Results A total of 211 infants were included in the study [gestational age 29 (27–31) weeks, birth weight 1140 (960–1340) g]. From these, 97 infants (46%) were given PTX treatment. The two groups were similar in terms of demographic data and baseline clinical characteristics. Any stage of ROP was detected in 47.4% of infants in the PTX group, which was significantly higher than those in the non-PTX group (27.2%) (p = 0.002). The incidence of advanced-stage ROP in the PTX group (10.3%) was also higher than in the non-PTX group (2.6%) (p = 0.021). Repeated usage of PTX was not found to be related to the development of ROP (p = 0.059). The time of PTX administration was similar between the ROP and no-ROP groups (median; one vs one week, p = 0.825). Surfactant therapy, duration of hospital stay, and PTX treatment were found as significant risk factors for ROP in the logistic regression analysis. Conclusions In contrast to the experimental studies and also promising results of PTX treatment in some neonatal morbidities, it may be associated with increased incidence and stage of ROP.