In this Progress Report, we update covalent chemical strategies commonly used for the focused functionalization of single‐walled carbon nanotube (SWNT) surfaces. In recent years, SWNTs have been treated as legitimate nanoscale chemical reagents. Hence, herein we seek to understand, from a structural and mechanistic perspective, the breadth and types of controlled covalent reactions SWNTs can undergo in solution phase, not only at ends and defect sites but also along sidewalls. We explore advances in the formation of nanotube derivatives that essentially maintain and even enhance their performance metrics after precise chemical modification. We especially highlight molecular insights (and corresponding correlation with properties) into the binding of functional moieties onto carbon nanotube surfaces. Controllable chemical functionalization suggests that the unique optical, electronic, and mechanical properties of SWNTs can be much more readily tuned than ever before, with key implications for the generation of truly functional nanoscale working devices. Rational covalent functionalization of single‐walled carbon nanotube (SWNT) surfaces can be used to carefully manipulate properties of SWNTs and enhance their performance in a wide range of diverse applications. In this review, we update on a number of diverse chemical strategies for productively functionalizing SWNTs at their ends, defect sites, and sidewalls. Potential applications in the fields of polymer composites and biological devices are also discussed.