Herein, reactivity studies of a cyclic bis‐hydridostannylene (ADC)SnH2 (1‐H2) (ADC=PhC{(NDipp)C}2; Dipp=2,6‐iPr2C6H3) with various unsaturated organic substrates are reported. Reactions of terminal alkynes (RC≡CH) with 1‐H2 afford mixed acetylide‐vinyl‐functionalized bis‐stannylenes via dehydrogenation and hydrostannylation. Treatment of 1‐H2 with PhC≡CCH3 gives a unique distannabarrelene via dehydrogenative C(sp3)−H stannylation and hydrostannylation of the C≡CCH3 moiety. 1‐H2 undergoes dehydrogenative 2+2‐cycloaddition reactions with diphenylacetylene, azobenzene, acetone, benzophenone, and benzaldehyde to form the 1,4‐distannabarrelene derivatives. The elimination of H2 in these reactions suggests the masked‐diradical property of 1‐H2. In fact, these 2+2‐cycloaddition products are also accessible on treatments of the Sn(I) diradicaloid (ADC)Sn2 (1) with appropriate reagents. All compounds have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction. Moreover, the catalytic activity of 1‐H2 has been shown for the hydroboration of unsaturated substrates. Reactivity (including catalytic activity) of hydridostannylene (1‐H2) with a variety of unsaturated (alkyne, carbonyl, azo) substrates has been reported. 1‐H2 (e. g.) undergoes dehydrogenative 2+2‐cycloaddition with Ph2CO to form the 1,4‐distannabarrelene 1‐OCPh2, which readily liberates Ph2CO on exposure to H2 and regenerates 1‐H2. Thus, 1‐H2 behaves as a masked Sn‐diradicaloid 1 that also affords 1‐OCPh2 on treatment with Ph2CO.