This paper aims at experimental research of the effect of hybrid interface (carbon/glass fibers) on delamination resistance in unidirectional fiber reinforced polymer (FRP) composite laminates under the mode I opening load conditions. Three group of laminates exhibiting different combinations of reinforcing materials at delamination plane were tested. Critical strain energy release rates were determined by using the double cantilever beam (DCB) tests in accordance with the ASTM D5528 Standard. Values of the GIC were calculated by using classical data reduction schemes and they were compared with values obtained by using an alternative compliance based beam method (CBBM). For precise detection of delamination onset all tests were additionally supported by registration of the acoustic emission (AE) signal. Contribution of mixed-modes were evaluated by using numerical finite element analysis. Obtained outcomes revealed, that differences in the mode I c-SERR values obtained by using four different methods were insignificant. Moreover, the greatest value of the GIC was determined for laminates with hybrid interface and it was equal 0.24 N/mm.