With an estimated annual incidence of one million cases, leishmaniasis is one of the top five vector-borne diseases. Currently available medical treatments involve side effects, including toxicity, non-specific targeting, and resistance development. Thus, new antileishmanial chemical entities are of the utmost interest to fight against this disease. We have shown in previous studies that gold(I) complexes bearing N-heterocyclic carbene (NHC) ligands with nitrogen or sulfur containing side arms have interesting biological activities in the field of cancer, malaria and leishmaniasis. The present study evaluates the in vitro antileishmania effects on L.infantum axenic amastigotes and their cytotoxicity for the human Thp1 cell line of a new family of 6 new imidazolium salts and their corresponding neutral (NHC)Au(I)Cl complexes. All new compounds have been characterized by classical analytical methods and five gold complexes have been evidenced by X-ray structure determination. We showed that one proligand has moderate activity (IC 50 = 8.24 µM) while 4 of 6 gold complexes have IC 50 values in the µM range (0.15-1.3 µM) including 3 with SI's between 46 and 108. These results suggest remarkable leishmanicidal activity in vitro for 3 new neutral (NHC)Au(I)Cl complexes making them candidate for further in vivo studies which are under investigation.