Geminiviridae are ssDNA plant viruses whose control has both economical and agricultural importance. Their capsids assemble into two distinct architectural forms: (i) a T = 1 icosahedral and (ii) a unique twinned quasi-isometric capsid. Described here are the high-resolution structures of both forms of the maize streak virus using cryo-EM. A comparison of these two forms provides details of the coat protein (CP) and CP–CP and CP–genome interactions that govern the assembly of the architecture of the capsids. Comparative analysis of other representative members of Geminiviridae reveals structural conservation of 60–95% compared to a sequence similarity of 21–30%. This study provides a structural atlas of these plant pathogens and suggests possible antiviral-targetable regions of these capsids.