The emergence of Internet of Energy (IoE) paves the way for sustainable and green energy environments that reduce energy costs and integrate Renewable Energy Sources (RESs) as new sources of energy. Electric vehicles (EVs) are one of the main actors of IoE future. The emergence of EVs promises to reduce the environmental crisis (e.g., carbon emissions); however, their charging process will consume massive amounts of electricity and may affect the reliability of the Smart Grid (SG). Recently, vehicle-to-vehicle (V2V) electricity trading approach has gained momentum as a novel strategy that reduces the peak power consumption in SG. In this context, EVs compete to provide electricity with lower prices, while maintaining the V2V electricity trading system secure. However, they lack flexibility, transparency, and authenticity. More importantly, they are based on centralized models (i.e., EV aggregators) which introduce single-point-of-failure and may cause the collapse of the system. In this paper, we propose a fully decentralized blockchain-based system that allows for an automated, fair, and trustworthy V2V electricity trading system; it uses Ethereum’s smart contracts to realize the V2V electricity trading system in a fully distributed, transparent, secure, tamper-proof and trustworthy manner. The proposed system is implemented, tested, and deployed on the Ethereum official test network Ropsten. The experiment results show that the proposed solution achieves security, flexibility, efficiency, and cost effectiveness making it a promising solution to new decentralized V2V electricity trading systems in SG.