Effects of water absorption and thermal environment on compression after impact (CAJ) charac-teristics of CFRP laminates are studied. Specimens were immersed in 71°C water for 10, 000 hours (410 days) to quantify the ratio of water absorbed in the CFRP laminates. Water content of the specimen was 1.4 wt% after the water absorption test. Numerical simulation using FEM code was conducted to predict moisture diffusion based on the measured orthotropic diffusion constants. Then impact tests by the drop-weight were carried out at room temperature at normalized energy level of 3.3 J/mm. Compression tests after impact tests were carried out at various temperatures, i.e., RT, 32°C, 177°C, for water absorbed specimens, and -54°C, RT, 82°C, 121°C, 149°C, 177°C for dry specimens. Delamination area and the number of transverse cracks of the water absorbed CFRP were smaller than those of dry specimens. Such smaller delamination area of wet specimens provides higher CAI strength than dry specimens. CAI strength of the water absorbed CFRP decreased significantly at high temperature because the glass-transition temperature deteriorates seriously due to the water absorption.