Moisture absorption investigations were carried out on glass/epoxy and carbon/epoxy composites. Moisture absorption was observed to cause more pronounced degradation of the fiber/matrix interface in carbon/epoxy composites than glass/epoxy composites. This paper detailed the studies to verify the extensive interface degradation in moisture-absorbed carbon/epoxy composites. The study involved measuring the contact angle between the fiber and matrix, conducting Fourier Transform Infrared Spectroscopy (FTIR) analysis, and assessment of the tensile properties of post-cured carbon/epoxy composites after moisture absorption. The findings indicated potential issues with incompatible sizing or surface treatments on the carbon fibers. These factors were observed to affect both curing and moisture absorption processes, leading to increased interface degradation in the moisture-absorbed carbon/epoxy composites.