This study comprehensively analyzed NAC family genes in *Oryza sativa* (rice) and *Arabidopsis thaliana* (thale cress). The NAC domain, originally identified in petunia NAM and Arabidopsis ATAF1, ATAF2, and CUC2, is a plant-specific transcriptional regulator involved in various developmental stages and tissues. The researchers identified 75 predicted NAC proteins in rice and 105 in thale cress. These NAC domains were classified into two main groups and 18 subgroups based on sequence similarity. Differences in amino acid sequences between rice and thale cress were minimal. Additionally, 13 common sequence motifs were found in the C-terminal regions of predicted NAC proteins, which are likely diverged and correlated with NAC domain structures. The study discusses the relationship between NAC family protein structure and function, highlighting the importance of subdomains A, C, and D in DNA binding and the potential roles of subdomains B and E in diverse functions. The findings will aid in further functional analysis of NAC family genes.This study comprehensively analyzed NAC family genes in *Oryza sativa* (rice) and *Arabidopsis thaliana* (thale cress). The NAC domain, originally identified in petunia NAM and Arabidopsis ATAF1, ATAF2, and CUC2, is a plant-specific transcriptional regulator involved in various developmental stages and tissues. The researchers identified 75 predicted NAC proteins in rice and 105 in thale cress. These NAC domains were classified into two main groups and 18 subgroups based on sequence similarity. Differences in amino acid sequences between rice and thale cress were minimal. Additionally, 13 common sequence motifs were found in the C-terminal regions of predicted NAC proteins, which are likely diverged and correlated with NAC domain structures. The study discusses the relationship between NAC family protein structure and function, highlighting the importance of subdomains A, C, and D in DNA binding and the potential roles of subdomains B and E in diverse functions. The findings will aid in further functional analysis of NAC family genes.