In recent decades, much attention has been paid to using nanomaterials in the development of highly-sensitive sensors for environmental monitoring. This review describes how nanomaterials are being used to develop electrochemical sensing platforms for environmental analysis (air pollution, water quality, soil nutrients, and soil pathogens). In particular, we discuss the use of nanofabrication techniques (e.g., monolayer self-assembly, dropcasting, molecular imprinting, electrodeposition, in situ polymerization, hydrogenation, and 3D printing) in the fabrication of high-sensitive electrodes is addressed. The potential use of carbon, organic, inorganic, and hybrid nanomaterials in electrochemical sensing platforms and to enable automation, real-time detection, and multiplexed test development are also addressed. Recent applications of mobile, disposable, wearable, implantable, and self-powered electrochemical sensors for monitoring ions, particles, compounds, nutrients, microorganisms, and contaminants in real environmental samples are covered. Finally, the opportunities and challenges in nanofabrication high-performance electrochemical sensors and optimizing their performance in testing real samples are highlighted.