Geotechnical instruments are used widely as a complementary tool to geodetic methods in monitoring natural and man-made structures. This paper provides an overview of geotechnical instruments used in structural monitoring. The transducers commonly used in geotechnical instrumentation are first introduced. This is followed by an introduction of the various types of instruments including their working principles and applications. The advantages and disadvantages of geotechnical instruments when compared with geodetic methods in structural monitoring are finally discussed.