The nuclear factor-Y (NF-Y) transcription factor, also known as heme-activator protein (HAP) or CCAAT-binding factor (CBF), is a critical transcription factor widely present in eukaryotes. The number of NF-Y subunits has significantly increased in higher plants compared to animals and fungi. The NF-Y complex is composed of three subunits: (1) NF-YA; (2) NF-YB; and (3) NF-YC. NF-YB and NF-YC contain histone fold domains (HFDs), which can interact with NF-YA or other transcription factors, or directly bind to the promoter CCAAT box to regulate the transcription of downstream genes. NF-Y plays a significant role in various plant processes, including growth and development. This review elucidates the structural and functional aspects of NF-Y subunits, identified NF-Y complexes, and their molecular regulatory mechanisms. Understanding these facets of NF-Y provides valuable insights into advancing crop genetic improvement and promoting sustainable agricultural practices.