A series of mono and bis N-Mannich bases incorporating 3-(4-methylphenyl)-4-(substituted-1/4-ylmethyl) sydnone scaffolds were synthesized and tested for their antibacterial, antifungal, anticancer, and antiviral activities. Most of the compounds showed moderate-to-significant antibacterial and antifungal activities. The compounds did not show selective activity against HIV. Some of the compounds have been evaluated for anticancer activity, but they were found as poorly active. The structures of the synthesized compounds were elucidated by IR and NMR spectroscopy.