Psilocybin and its direct precursor baeocystin are indole alkaloids of psychotropic Psilocybe mushrooms. The pharmaceutical interest in psilocybin as a treatment option against depression and anxiety is currently being investigated in advanced clinical trials. Here, we report a biocatalytic route to synthesize 6-methylated psilocybin and baeocystin from 4-hydroxy-6-methyl-l-tryptophan, which was decarboxylated and phosphorylated by the Psilocybe cubensis biosynthesis enzymes PsiD and PsiK. N-Methylation was catalyzed by PsiM. We further present an in silico structural model of PsiM that revealed a well-conserved SAM-binding core along with peripheral nonconserved elements that likely govern substrate preferences.