Poly(propylene imine) (PPI) dendrimers contained surface maltose modification are proposed as drug carriers for nucleoside analog (NA) 5′-triphosphates. The aim of this study was to investigate the interactions between PPI dendrimers of 3rd (G3) or 4th (G4) generation and cytidine-5′-triphosphate (CTP) by Isothermal Titration Calorimetry method. CTP was used as a model molecule of pyrimidine nucleoside analog - cytarabine (ara-CTP) commonly used in leukemia treatment. Complexes of PPI dendrimers with NAs may help to overcome severe limitations of NAs associated with their low solubility and stability or resistance in cancer cells. In the present work, we evaluated stoichiometry and a mechanism of forming complexes between dendrimers and the nucleotide. Moreover, we examined the efficiency of complex formation in relation to dendrimer generations, a type of dendrimer modification with maltose residues and a type of solvent. It was observed that PPI dendrimers create complexes with CTP with high efficiency that makes them promising candidates for a drug delivery system.