Poly(propylene imine) (PPI) glycodendrimers are promising candidates as drug carriers and anti-amyloidogenic and anti-prionic agents. In this study the anti-β-amyloid capacity of PPI glycodendrimers of the 4th and 5th generations was investigated in vitro and in vivo. We assessed distinct PPI glycodendrimers including G4mDS and G5mDS, with electroneutral maltose shell, and G4mOS and G4m-IIIOS, with cationic maltose or maltotriose shell. Our results show that in vitro PPI maltose dendrimers reduce the toxicity of Aβ(1-42). However, only the electroneutral maltose dendrimers G4mDS and G5mDS reduce the toxicity of Alzheimer's disease brain extracts in SH-SY5Y neuroblastoma cells. PPI maltose dendrimers with electroneutral or cationic surface penetrate the cytoplasm of cultured cells, and they reach the brain when administered intranasally. Both cationic G4mOS and electroneutral G4mDS are able to modify the total burden of β-amyloid in APP/PS1 mice. The studied dendrimers did not reverse memory impairment in APP/PS1 mice following chronic administration; moreover, cationic G4mOS caused cognitive decline in non-transgenic mice. In spite of the capacity of G4mDS and G4mOS to cross the blood brain barrier and modulate Aβ aggregation in APP/PS1 mice, further studies are needed to learn how to reduce the harmful effects of maltose dendrimers in vivo.