Theory of low‐voltage (LV) Cs–H2discharge is presented. LV arc plasma is created in consequence of ionization of small Cs amount (NCs/NH2≲10−2), hydrogen being non ionized and slightly dissociated. In dense LV plasma the cathode beam relaxation and thermal electron heating occur because of pair Coulomb collisions between beam and plasma electrons. The volume H−generation occurs because of dissociation attachment of heated thermal electrons to vibrationally excited H2molecules. It is shown theoretically that high H−concentration (NH−≳1013cm−3) may be achieved in dense plasma of LV Cs–H2discharge. The high rate of H−generation is explained by optimum value of thermal electron temperature (Te≳1 eV), high electron concentration (n∼1014cm−3) and high hydrogen pressure (PH2≳1 Torr), that causes rapid v‐v pumping of vibrationally excited H2levels. Results of the first experimental investigation of LV Cs–H2discharge are presented. It is shown that LV discharge exists at comparatively small anode voltage (Ua≳1 V) and sufficiently high electron temperature and concentration. Preliminary comparison between theoretical and experimental data is fulfilled. Experimental plasma parameters agree satisfactory with theoretical ones.