The effect of hygrothermal pre-conditioning on the fatigue delamination growth onset of bonded joints under pure Mode I and II was investigated. The fatigue tests were conducted on CFRP epoxy joints with an epoxy interleaf that were subjected to a relative humidity (RH) of 90% and at a temperature of 80°C until steady state saturation. For both loading configurations, three types of joining techniques were evaluated: co-curing, co-bonding and secondary bonding. The co-bonded (CB) and secondary bonded (SB) specimens contain an epoxy adhesive film, while the co-cured (CC) specimens were only comprised by fibers and resin. The Mode I and II G-N curves were obtained using double cantilever beam (DCB) and three point bend end-notched flexure (3-ENF) testing, respectively. Through the G-N curves, the threshold (Gth) value of each bonding technology was estimated and compared with dry specimens. Finally, the strain energy release rate (SERR) results were related with the joint's failure mechanism through a fractographic analysis. Under both loadings modes, the adhesive joints experienced a significant decrease in their Gth values in comparison with the dry joints. Water uptake degrades the adhesive and adhesive/substrate interface and causes the polyester net's swelling, which favors the water diffusion through the laminate. For Mode I loadings, the CC aged joints experienced a Gth increase of 17.39% in comparison with the dry joints due to the increase of the interleaf plastic deformation. While, under Mode II loadings, the CC aged joints present a slight decrease of 1%. For Mode I loading, the aged CB joints present a better fatigue delamination growth onset than the aged CC and SB joints, while, for Mode II the aged CC joints exhibited a Gth value approximately 2 and 4 times higher than the aged CB and SB joints, respectively