Tetramethylammonium hydroxide (TMAH) thermochemolysis has been utilized by the Curiosity rover’s Sample Analysis at Mars (SAM) instrument and will be utilized by the ExoMars 2022′s Mars Organic Analyzer (MOMA) instrument. TMAH thermochemolysis is one of the main techniques that enables the detection of bioindicators when it is combined with pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) at the surface of Mars. This study identifies the thermochemolysis products of targeted nucleosides using flash pyrolysis and a SAM-like ramp pyrolysis. Results indicate that the methylated nucleosides can be detected when nucleosides are submitted to TMAH thermochemolysis, which demonstrates that the TMAH thermochemolysis protocol does not result in the decomposition of the nucleosides. To detect the whole structure of each nucleoside, low thermochemolysis temperature is required. 200 °C is the optimal temperature. Methylated nucleobases are the main products of the tested nucleosides when the thermochemolysis temperature is higher than 300 °C. Furfuryl methyl ether, one of the degradation products of these nucleosides, were also identified from 200° to 600°C in this study. These experiments will establish a reference database for interpretation of the data acquired by the SAM and MOMA experiments during operations on Mars. •Six nucleosides were analyzed under conditions relevant to Mars’ instrument.•The methylated nucleosides were detected first under SAM-like ramp pyrolysis.•The TMAH thermochemolysis byproducts of six nucleosides were determined.•No interaction was found among the nucleoside mixtures.•200 °C is the optimal thermochemolysis temperature for nucleosides and 600 °C for nucleobases.