An efficient protocol for synthesis of 3,3'-diindolylmethanes using recyclable Fe-pillared interlayered clay (Fe-PILC) catalyst under aqueous medium has been developed. All synthesized 3,3'-diindolylmethanes showed promising antileishmanial activity against Leishmania donovani promastigotes as well as axenic amastigotes. Structure-activity relationship analysis revealed that nitroaryl substituted diindolylmethanes showed potent antileishmanial activity. The 4-nitrophenyl linked 3,3'-diindolylmethane 8g was found to be the most potent antileishmanial analog showing IC50 values of 7.88 and 8.37 μM against both L. donovani promastigotes and amastigotes, respectively. Further, a pharmacophore based QSAR model was established to understand the crucial molecular features of 3,3'-diindolylmethanes essential for potent antileishmanial activity. These compounds also exhibited promising antifungal activity against Cryptococcus neoformans, wherein fluorophenyl substituted 3,3'-diindolylmethanes were found to be most potent antifungal agents. Developed synthetic protocol will be useful for economical and eco-friendly synthesis of potent antileishmanial and antifungal 3,3'-diindolylmethane class of compounds.