Gender is by far the most complex and multilayered theme that Parker-Chan explores in She Who Became the Sun. On one hand, they discuss the traditional gender roles and the treatment of each within Mongol and Nanren societies; on the other, they explore individual gender identity and fluidity.

Both the Yuan dynasty and the Nanren society in the south are patriarchal. Sons inherit from their fathers. This can be seen in Zhu’s childhood and her father’s favoritism toward her brother, but also in Esen’s struggles to sire a son, to the point that he considers adoption. Esen is also dismissive of his wives, calling Ouyang lucky because, as a eunuch, he will never marry or have children. On the other hand, Ma Xiuying is distinctly aware of the limitations of women within Red Turban society. Although she is well-educated and comes from a good background, her advice is either ignored or assuaged by promises of male-dominated victory. Left Minister Chen notices her actions only so he can prevent her from warning Little Guo. Only Zhu (who has experienced both gender roles) seeks her out and considers her advice useful. Although Zhu initially encourages Ma to follow her desires rather than resign herself to the domestic duties society expects, by the end of the novel Ma succumbs to Zhu’s desire for the throne.