Bunsen's cacodyl disulfide, Me2As(S)‐S‐AsMe2 (1), reacted with iodine giving the novel dimethylarsinosulfenyl iodide, Me2As‐S‐I (3) although theoretical calculations indicated that the AsV compound Me2As(S)‐I (4) was more stable in the gas phase. The oily product was stable neat and as a solution in CDCl3 at +4 °C and –20 °C for at least 15 d. Light, H2O, H2O2, and Zn dust, but not NaI or Ag, decomposed it. Compound 3 did not interact with Ph3N, with Ph2NH and PhNH2 it interacted but not reacted. 3 was decomposed by piperidine, with pyridine and 4‐dimethylaminopyridine it interacted and produced Me2As‐SS‐AsMe2 (2) and I2 that formed charge transfer complexes Base·I2, whereas Et3N decomposed 3, and 3Et3N·2I2 was isolated. 3 was desulfurized by Ph3P and (Me2N)3P completely, and by (PhO)3P and (PhS)3P partially. The reactions of 3 with (Me2N)3P, (PhS)3P, and (EtO)3P were complicated. From the AsIII nucleophiles, only Ph3As was bound, while (PhS)3As reacted slowly in a complicated manner with 3. No interaction of 3 with MeOH or PhOH was observed but NaOH, Ag2O, and PhONa decomposed it. Thiophenol produced traces of Me2As‐SPh (10) and sodium thiophenolate attacked mainly at AsIII of 3. Thus, externally stabilized sulfenium ions of the type Me2As‐S‐Nu+I– were not obtained.