Monomodal colloidal suspensions containing EDI-type zeolite nanocrystals with sizes below 20 nm were prepared via a palladium and platinum amine templating approach. The role of the metal complexes in zeolite crystallization is elucidated using spectroscopic and microscopic characterization techniques in a series of samples containing pure Pd, Pt, and Cu amine complexes as well as mixtures of two compounds. The crystallization process of colloidal zeolites in precursor suspensions containing both [Pd(NH3)4]2+ and [Pt(NH3)4]2+ proceeds faster than in [Cu(NH3)4]2+ systems. The Pd and Pt complexes lead to a faster and enhanced nucleation rate in the precursor aluminosilicate suspensions in comparison to the copper amine complex. The latter explains both the smaller particle size and the higher monodispersity in the samples templated by Pd and Pt as compared to pure Cu-containing samples. Precursor systems containing mixed metal templates were used to control further the particle size and degree of metal loadings in the colloidal molecular sieves.