Telomerase is a ribonucleoprotein reverse transcriptase that is responsible for maintaining the telomere length in cells. Telomerase overexpresses in almost all malignant tumor cells, and it has become a promising biomarker and a potential therapy target for cancers. Consequently, accurate and efficient quantification of the telomerase is highly essential to medical diagnostics and therapeutics. Recently, a series of novel telomerase detection methods with excellent performance have been developed, but a overview of in vivo telomerase detection methods is lacking. In this Minireview, we summarize the emerging strategies for telomerase assays in the last five years, including both in vitro assays and in vivo imaging methods, and discuss their future directions as well.