The alkaline degradation of cellobiose (4-O-β-D-glucopyranosyl-D-glucopyranose) under nitrogen atmosphere at varying pressures (1, 5, and 10 bar) and temperatures (20, 35, and 50 °C) was studied. The degradation was carried out in a microreactor (50 mL) and the samples were taken after a reaction time of 2, 4, 6, 8, and 24 h. Non-oxidized degradation products were determined and identified by gas chromatography-flame ionization detection/mass selective detection (GC-FID/MSD) as their per(trimethylsilyl)ated derivatives. The most prominent products were α- and β-glucoisosaccharinic acids (38.2−59.1% of the measured products after 24 h), lactic acid (5.5−33.9%), and glucose (10.4−39.4%) together with minor amounts of methylglyceric acid, 2-hydroxybutanoic acid, 2,4-dihydroxybutanoic acid, 2,5-dihydroxypentanoic acid, anhydroisosaccharinic acid, 3-deoxy-hexonic acid, mannose, and fructose. An increase in the nitrogen gas pressure had only a slight effect on the product formation, but higher temperatures clearly favored the conversion reactions; after a reaction time of 24 h at varying pressures the content of all the reaction products formed were at 20, 35, and 50 ^oC, respectively, 65.3−77.9, 82.6−84.2, and 82.5−91.8% of the initial cellobiose.