This study analyzed the potential reduction in environmental impact achieved by repurposing waste fishing nets, which constitute half of marine debris, as concrete fiber reinforcement. Using a life cycle assessment methodology, the entire process was evaluated. Additionally, a cost-benefit analysis (B/C analysis) was conducted to assess the feasibility of the fishing net recycling project. The environmental impact analysis revealed the most significant reduction occurring in the acidification potential (AP) category, with a decrease of 1.13E-01 kg SO₂-eq., indicating a reduction rate of 93.81%. Other notable reduction percentages were found in photochemical smog (POCP) at 8.14E-03 kg C₂H₄-eq. (69.54%) and eutrophication (EP) at 9.81E-03 kg PO₄ ^3-eq. (51.08%). The reductions in global warming potential (GWP), ozone depletion potential (ODP), and abiotic depletion potential (ADP) were relatively lower at 8.03E+00 kg CO₂-eq. (5.43%), 3.86E-08 kg CFC-11-eq. (2.03%), and 8.48E-03 kg Sb-eq. (2.14%), respectively. Furthermore, with raw material acquisition costs set at 10% of the price per ton of new nylon (approximately 2.8 million KRW) and post-processing recycled product sales prices at 60% of the new product price, the B/C ratio was calculated to be 3.00. Given these parameters and assuming complete sales of waste fishing net flakes, the average annual expected profit amounts to KRW 1,086.5 million, with a projected total profit of KRW 5,432.6 million over five years. This study represents the first analysis of both the environmental and economic impacts of recycling waste fishing nets as concrete reinforcement. Its significance lies in its ability to quantify and visualize the environmental impact avoidance resulting from waste resource utilization. Furthermore, given the gradual progress in the recycling of discarded fishing nets, the findings of this study are anticipated to serve as valuable foundational research data for designing domestic marine waste management measures.