Microfluidics is an emerging field with various applications. In situ analysis of liquids inside microfluidic channels is an important research subject for any of these applications. On the other hand, attenuated total reflectance infrared spectroscopy (ATR-IR) is a strong surface detection method. Recently, there have been various attempts to use ATR-IR for detection of liquids inside microfluidic channels. Micromachined silicon ATR-IR (Si-ATR-IR) is an emerging analytical tool for micro/nanofluidics. This paper reviews Si-ATR-IR micro/nanofluidics detection devices and discusses the application fields, capabilities, advantages, and disadvantages of the method.