Biofuel production from microalgae is considered as a promising strategy for alternative and eco-friendly energy production, but is still challenged by problems including economic deficit. These problems can be solved by genetic modifications resulting in increased lipid productivity. Transcription factors (TFs) are emerging as candidates of genetic engineering of microalgae since they are involved in various metabolic pathways in organism. Among transcription factors, we investigated basic Leucin Zipper (bZIP) in Chlorella sp. HS2 since bZIP family is known as a key regulator of lipid biosynthesis in plants and other microalgae. In this study, we overexpressed HSbZIP1 TF and transformants showed enhanced biomass and lipid biosynthesis. In addition, we confirmed that expression levels of genes regulated by HSbZIP1 TF were up-regulated consistently during cultivation. Taken together, these results suggest that HSbZIP1 TF also plays an important role in lipid biosynthesis of Chlorella sp. HS2.