The family Tolecusatellitidae comprises of the biological satellites that are not assigned to any higher taxonomic rank. Satellites are nucleic acids that rely on their helper viruses to replicate and proliferate, yet they display no sequence identities with their associated viruses. The family Tolecusatellitidae consists of two genera: Betasatellite and Deltasatellite. Since the discovery of the first geminivirus-associated satellite, tomato leaf curl virus-satellite (ToLCV-sat) in 1997, an increasing number of evidences have suggested that satellites play vital roles during geminiviral infections (Dry et al. 1997; Fauquet et al. 2005; Zhou 2013; Fiallo-Olivé and Navas-Castillo 2020). In response to the increasing number of satellites that have been identified, a proper classification and nomenclature is needed to properly identify/describe the satellites. Taxonomically, the satellites of the genera Betasatellite and Deltasatellite are placed in the same family because they are thought to have been originated and subsequently diverged from a common ancestor (Lozano et al. 2016). A new genus was proposed for true satellites associated with geminiviruses. The proposed genus includes satellites that resemble betasatellite molecules that are defective in some respects (betasatellites lacking the βC1 gene). Deltasatellites include A-rich sequences and satellite-conserved region/SCR-associated sequences related to the betasatellites. However, SCR-like sequences of deltasatellites differ from defective forms of betasatellite molecules that include insertions and deletions compared to betasatellites. In addition, defective betasatellites are always accompanied by the parent (full) betasatellites. Until now, no study has reported on the coexistence of betasatellite and deltasatellite (Nawaz-ul-Rehman et al. 2021). Most satellites interfere with helper virus replication and reduce symptoms. Some satellites exacerbate the symptoms of helper virus-induced infection or cause new symptoms usually not related to the helper virus infection. Satellites might function in determining the host range or effectiveness of helper virus transmission (Fiallo-Olivé et al. 2016; Nawaz-ul-Rehman et al. 2021). The family Tolecusatellitidae consists of two genera: Betasatellite, which encompasses 119 species, and Deltasatellite, which has 12 species ( https://ictv.global/taxonomy ) (Fig. 37.1 and Table 37.1).