Cocconeis neodiminuta is a small, adnate diatom in the family Cocconeidaceae, distinguished from related species within the genus by its diminutive frustule size and specific silica wall ornamentation patterns resolvable by electron microscopy. As a member of the genus Cocconeis, this species is an epiphytic organism that lives attached to the surfaces of aquatic plants, filamentous algae, sediment particles, and submerged solid substrates in freshwater and occasionally brackish environments. The frustule—the intricate silica cell wall that encases the diatom cell—consists of two overlapping halves (valves) with species-specific striation patterns and pore fields (areolae) used in taxonomic identification. Cocconeis neodiminuta has been documented from freshwater environments across South America and various other regions, suggesting a broad cosmopolitan distribution consistent with many freshwater diatom taxa. The species, like other cocconeid diatoms, reproduces primarily by asexual binary fission, with periodic sexual reproduction through auxospore formation to restore cell size after successive divisions cause progressive size reduction. As a photosynthetic primary producer in benthic communities, this diatom contributes to the base of aquatic food webs and participates in the biological cycling of silicon—an element critical to diatom frustule production and removed from solution as diatoms proliferate. Its conservation status has not been evaluated by the IUCN.