Phthalate plasticizers used in a wide range of common plastic products are released into the environment and may pose a risk of increased incidence of type 2 diabetes. In this work, we studied the effects of monoethyl phthalate (MEP), the metabolite of diethyl phthalate, exposure on 1.1B4 human pancreatic beta cells at low doses (1-1000 nM). We showed that MEP treatment induced proliferation in 1.1B4 cells. Also PCNA protein expression levels were increased related to proliferation induction. It has been noted that phthalates can exert estrogen mediated response by interacting with ER. In our study 24 h MEP treatment decreased ER alpha protein expression level conversely it increased the same protein expression level after 72 h treatment. Also MEP treatment decreased ER beta expression after 72 h at 1.1B4 cells. Our results further show that insulin content of 1.1B4 cells were increased with low dose MEP treatment. Along with our insulin content results, PDX-1 expression levels were also increased at 1.1B4 cells with MEP treatment. These findings suggest that MEP acts as an estrogenic compound and PPAR gamma agonist at lower concentrations. Also it should be noted that PDX-1 may be a critical regulator of 1.1B4 cells treated with MEP. (C) 2016 Elsevier Ltd. All rights reserved.