Nanofluids offer many opportunities to enhance the efficiency of thermal systems by improving the thermal properties of the host fluids. Due to its exceptional thermal, mechanical and electrical properties, diamond has attracted attention for use as a nanoparticle in fluids. Thereby, nanofluids have proven to be useful in applications, especially electronic cooling, where increasing thermal properties and avoiding electrical conductivity are vital. There have been numerous investigations of nanodiamond-nanofluid systems with many suggesting that considerable property enhancements, e.g., increased thermal conductivity, might be possible. However, those results have not been collectively compared or discussed. This paper reviews and summarizes the experimental values of the physical and thermal properties, including an appropriate focus on the thermal conductivity enhancement, of nanodiamond-nanofluid systems found in the literature as well as different techniques for thermal conductivity measurement. The effect of various factors on the thermal-physical properties of diamond nanofluids is also reviewed, and the stability and viscosity of diamond nanofluids are tabulated and compared. The preparation and properties of hybrid nanofluids containing diamond nanoparticles are analyzed and discussed in detail, and a list of potential uses for these enhanced heat transfer fluids in industrial and commercial applications is provided and deliberated. (C) 2018 Elsevier Ltd. All rights reserved.