To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall–degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7–38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a ‘symbiosis toolkit’, with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes. ; This material is based on work conducted by the US Department of Energy Joint Genome Institute, a DOE Office of Science User Facility, supported under contract no. DE-AC02-05CH11231. This work was also supported by the Laboratory of Excellence ARBRE (ANR-11-LABX-0002-01), the Genomic Science Program (Plant-Microbe Interactions project) funded by the US Department of Energy, Office of Science, Biological and Environmental Research (contract DE-AC05-00OR22725), the Lorraine Region Council (to F.M.), US National Science Foundation grants DEB-1208719 and DEB-0933081 (both to D.S.H. and DEB-1021606 (to A.P.)), the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG FTZ 118) and the German Science Foundation (DFG, grant BU941/20-1) (to F.B.) and the Swedish Research Council (to A. Tunlid). This work was partly supported by the Laboratory of Excellence TULIP (ANR-10-LABX-41 and ANR-11-IDEX-0002-02). F.M. would like to acknowledge M.A. Selosse and B. Lindahl for helpful discussions.