Glioblastoma is characterized by heterogeneous malignant cells that are functionally integrated within the neuroglial microenvironment. Here, we model this ecosystem by growing glioblastoma into long-term cultured human cortical organoids that contain the major neuroglial cell types found in the cerebral cortex. Single-cell RNA-seq analysis suggests that, compared to matched gliomasphere models, glioblastoma cortical organoids (GCO) more faithfully recapitulate the diversity and expression programs of malignant cell states found in patient tumors. Additionally, we observe widespread transfer of glioblastoma transcripts and GFP proteins to non-malignant cells in the organoids. Mechanistically, this transfer involves extracellular vesicles and is biased towards defined glioblastoma cell states and astroglia cell types. These results extend previous glioblastoma-organoid modeling efforts and suggest widespread intercellular transfer in the glioblastoma neuroglial microenvironment.