A carbon fiber and epoxy composite material was studied for the effects on enhancing the structural integrity of a pipeline with defected girth weld joints in sub-zero conditions via finite element analysis (FEA) and experimentally on full-scale pipe spools. Linear Finite Element Analysis simulations were performed to evaluate the composite reinforcement of a crack in the girth weld. Experimental testing was carried out on 24 inch (600 mm) diameter pipe spools at -20ºC with a simulated through-wall crack and strategically located tack welds to hold the two spools together. Two configurations of the pipe were tested, leaking and non-leaking. The leaking configuration was tested using four different repair configurations. An engineered composite wrap design was installed and subsequently tested to the maximum pressure on a test spool designed to simulate a failed weld, under conditions provided by an interested end user. Strain gauges were used to quantify the composite repair system's effectiveness at low temperature (-20 ºC) and high-pressure (32 bar) conditions. Both finite element analysis results and full-scale testing demonstrated that the composite repair system is capable of sealing and successfully reinforcing simulated through-wall cracks in vintage girth welds. Based on the testing, an end user decided to implement the repair system for their defected vintage girth welds. The successful field implementation and logistics for repairing the end user’s girth welds are also discussed.