A series of new (1,3,4-thiadiazin-2-ylamino)isoindoline-1,3-dione derivatives 5, 8, 9, 11a-d, and 13a,b were prepared via one-pot three component reaction of isobenzofuran-1,3-dione 1, thiocarbohydrazide 2 and various alpha-halocarbonyl compounds. The chemical structure of the new compounds was elucidated by spectral analyses and X-ray single crystal technique. The newly synthesized compounds were also evaluated for their in vitro antimicrobial activity, and showed promising results.