The use of composite materials for repair and rehabilitation of corroded steel pipes has been increasingly growing in the oil and gas industry. However, there exists a noticeable gap in the literature on the long term performance of composite repaired pipes, especially those subjected to large internal pressure magnitudes. This work is an attempt toward filing the gap by gaining a better understanding of the effects of environmental conditions on the long term performance of composite repaired pipes subjected to large internal pressures. Finite element method (FEM) is used to simulate typical composite warp-repaired gouged steel pipes, conditioned in various environments and subsequently subjected to internal pressure. The influence of the resulting degradation in composite’s mechanical properties on the performance of the system was evaluated. To validate the results, an experimental program was designed and carried out. Repaired specimens were conditioned in an environmental chamber under certain thermal and moisture conditions; then, the specimens were tested to failure subject to internal pressure. Good correlation was obtained after fine tuning of FEM model’s material data through the use of the experimentally obtained data.