The leaf, twig, and nodal anatomy of Alzatea, Axinandra, Crypteronia, Dactylocladus, and Rhynchocalyx is described in detail. This family, as newly delimited by Van Beusekom-Osinga and Van Beusekom, appears to be very heterogeneous, a conclusion supported by the wood anatomical diversity reported in another paper. The nodes may be simply unilacunar, unilacunar with a complete girdling trace, of the common gap (or split lateral) plus median trace type, or trilacunar. Cortical bundles may be present in addition. Further diversity is present in e.g. cuticular texture, stomatal type, hypodermal development, arrangement of vascular bundles in petiole and midrib, mechanical support of the veins, the crystal complement, foliar sclereids, and cork origin. Anatomical evidence only supports the Myrtalean character of all genera, and a close mutual affinity of Axinandra and Crypteronia. These genera, together with Dactylocladus show several features characteristic for some Melastomataceae, which family with its wide anatomical range would also cover most of the anatomical diversity of Lythraceae, Sonneratiaceae, Oliniaceae, Alzatea, and Rhynchocalyx. Rhynchocalyx appears to be closer in its anatomy to some Lythraceae, Oliniaceae, and Melastomataceae than to the other members of Crypteroniaceae. Alzatea shows affinities with all families mentioned, but remains problematic with its trilacunar node not known to occur in the other families. The complex pattern of overlapping anatomical ranges of Crypteroniaceae s.l., Melastomataceae, Lythraceae, Oliniaceae, and Sonneratiaceae may be interpreted as evidence of intimate relationships between these families.