Recent research trends in biosensing have been geared toward developing bioanalytical devices that are label free, small in size, and portable and that can operate in a rapid manner. The performance of these devices has been dramatically improved through the advent of new materials and micro-/nanofabrication technologies. This is especially true for micro-/nanosized cantilever sensors, which undergo a change in mechanical properties upon the specific binding of biomolecules. In this review, we introduce the basic principles of cantilever biosensors in static and dynamic modes. We also summarize a range of approaches to cantilever design, fabrication, and instrumentation according to their applications. More specifically, we describe cantilever-based detections of proteins, DNA molecules, bacteria, and viruses and discuss current challenges related to the targets' biophysical characteristics.