The use of guided wave testing (GWT) for the inspection of composite materials presents several challenges due to variations in wave speed and signal attenuation for different fiber orientation. This study presents a strategy to detect and locate defects in composite materials using ultrasonic guided wave (UGW) testing with a network of piezoelectric transducers (PZT) sensors arranged in a square configuration. Instead of using all possible sensor combinations in the network of PZT sensors to detect and locate a defect in the monitored region, only UGW signals from pairs of sensors that share identical distances and path conditions were recorded for defect localization. To simulate different defect locations, magnets were attached to the CFRP surface at different locations to create perturbations in the wave propagation path. The reconstruction algorithm for probabilistic inspection of defects (RAPID) algorithm was adopted as an image processing procedure for defect detection and localization in the CFRP specimen.