Colloidal quantum dots (QDs) are a fascinating class of semiconducting nanocrystals, thanks to their optical properties tunable through size and composition, and simple synthesis methods. Recently, colloidal double‐emission QDs have been successfully applied as competitive optical temperature sensors, since they exhibit structure‐tunable double emission, temperature‐dependent photoluminescence, high quantum yield, and excellent photostability. Until now, QDs have been used as nanothermometers for in vivo biological thermal imaging, and thermal mapping in complex environments at the sub‐microscale to nanoscale range. In this Review, recent progress for QD‐based nanothermometers is highlighted and perspectives for future work are described.