Translation elongation factors (EFs) are proteins that play important roles during the elongation stage of protein synthesis. In prokaryotes, at least four EFs function in repetitive reactions (EF-Tu, EF-Ts, EF-G, and EF-P). EF-P plays a vital role in the specialized translation of consecutive proline amino acid motifs. It was also recently recognized that EF-P acts throughout translation elongation. Here, we demonstrated for the first time that cell division and morphology are intimately linked to the control of EF-P in the model cyanobacteriumSynechococcus elongatusPCC7942. We constructed the overexpression of a wild-type gene product for EF-P (Synpcc7942_2565) as a tool to identify EF-P functionality. The overexpression of EF-P resulted in the morphological plasticity of hyperelongated cells. During the stationary phase, EF-P overexpressors displayed cell lengths of 150 mu m or longer, approximately 35 times longer than the control. Total cellular protein and amino acid content were also increased in overexpressors. To explore the molecular mechanisms underlying hyperelongation, gene expression analysis was performed. The results revealed that cell division genes, includingftn6,minD,mreB,mreC, andftsZ, were modulated in overexpressors. Strikingly,ftn6was severely down-regulated. Little is known regarding EF-P in prokaryotic photosynthetic organisms. Our results suggest that cyanobacterial EF-P participates in the acceleration of protein synthesis and also regulates cell division processes. These findings suggest new ways to modify translation and metabolism in cyanobacteria. Phenotypic and metabolic alterations caused by overexpressing EF-P may also be beneficial for applications such as low-cost, green molecular factories.