This paper aims to measure efficiency of utilizing resources in implementing green supply chain management (GSCM) strategy. Data Envelopment Analysis (DEA) is used to assess how firms convert firm’s resources (inputs: 1) cost for ISO 14000 implementation project/annual expense; 2) frequency for auditing with supplier) to generate two outputs (cost for energy consumption, and cost of waste treatment). Nine firms in electronic parts/components manufacturing industry that have been implementing this strategy are selected as case examples. Results of real operating data from 9 cases reveal that 5 firms are efficiently managing their resources to achieve expected benefits of GSCM strategy, whereas the remaining 4 firms are considered inefficient in term of utilizing internal resources to operate their GSCM. Not only does the DEA analysis identify the GSCM good practices among all firms, this technique also demonstrates causes of inefficiency for 4 inefficient firms for any opportunities for improvement.