This large international mega-analysis combined 11 rsfMRI datasets across five classic psychedelics to identify consistent effects on brain connectivity. Across drugs, psychedelics robustly increased functional connectivity between higher-order (transmodal) and sensory (unimodal) brain networks, while producing weaker and more variable reductions within networks. Subcortical regions—especially the caudate and putamen—also showed altered coupling with cortical systems. Overall, the findings suggest that psychedelics reorganize large-scale brain networks by enhancing cross-network communication rather than broadly disrupting internal network structure.