The marine-derived indole alkaloids meridianin C and G and their N1-substituted and C-ring modified analogs were synthesized and screened for antiprotozoal and antimicrobial activities. Meridianin C and G showed antimalarial activity against both chloroquine-resistant (D6) as well as sensitive (W2) clones of Plasmodium falciparum with IC50 values in the range of 4.4 to 14.4 mM. Meridianin G showed better activity against the W2 clone, showing a higher selectivity index >24.1. Among the analogs, the N1-morpholinoyl meridianin C analog displayed antimalarial activity against both clones, showing selectivity indices up to 25.1. Meridianin C along with a few other analogs showed weak to moderate antileishmanial activity against Leishmania donovani promastigotes, the best analog being a C-ring modified 5-iodo meridianin showing an IC50 of 9.17 mM. A few compounds also showed mild antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus, and antifungal activity against Cryptococcus neoformans.