Accumulating evidence has linked G-quadruplex structures to a number of biological processes in vivo, including DNA replication, transcription, and genomic maintenance. However, the precise function and mechanism of G-quadruplex formation in mammalian cells remains poorly defined. Therefore, the development of small-molecule G-quadruplex probes has attracted significant attention in recent years. This review highlights examples of G-quadruplex probes that have been reported over the last few years, some of which have been employed for cellular imaging or for use in the construction of G-quadruplex-based analytical sensing platforms.