•The experimental investigation of fracture in PMMA (Polymethyl-methacrylate) plate specimens under mode I was carried out.•The stress and strain field distribution under the critical load value was calculated using Finite Element Method (FEM).•The stress–strain criterion for notched specimens under tension was proposed. This paper shows the results of experimental and numerical investigation of fracture in PMMA (Polymethyl-methacrylate) plate specimens under mode I. Samples had two thicknesses (9.7 and 18 mm) and they were weakened by two types of edge-notches: rounded V-notch with radius 0.5 mm and U-notch with radius 10 mm. During tests, critical load value, fracture initiation point and fracture initiation angle were obtained. Additionally, the fracture process was recorded by a high-speed PHANTOM camera. Crack length growth and changes in crack tip velocity over time were analyzed. Stress and strain fields under the critical load value were calculated using Finite Element Method (FEM). Three-dimensional isoparametric elements were used and non-linearity of material and geometry was also included. A stress–strain criterion for notched specimens under tension was proposed.