Abstract We report on the shell-to-core carrier-transfer in GaAs/Al0.1Ga0.9As core-shell nanowires grown on Si(100) substrates via molecular beam epitaxy. The nanowires are dominantly zincblende and are tilted with respect to the substrate surface. Photoluminescence (PL) excitation spectrosocopy at 77K revealed an abrupt increase in the GaAs PL intensity at excitation above the Al0.1Ga0.9As shell bandgap which is attributed to shell to core carrier-transfer. More carriers from the Al0.1Ga0.9As transfer to the GaAs at T>90K, as observed in the time-resolved PL and temperature dependence of the relative PL intensities of GaAs and Al0.1Ga0.9As due to the ionization of the traps within the Al0.1Ga0.9As. Using a coupled rate equation model that takes into account shell to core carrier-transfer, the average recombination time constants of Al0.1Ga0.9As shell τrec,s=400ps (580ps) and GaAs core τrec,c=600ps (970ps) were obtained from the time-resolved PL at 300K (77K). Carrier-transfer time constants τCT=50ps (55ps) at 300K (77K) were also obtained.