The dyeing of meta-aramids (m-aramids) has conventionally been difficult due to their rigid molecular and dense crystalline structure that results from hydrogen bonding, although various dyeing techniques have been applied in the past to improve their dyeability. In this study, m-aramid nanofibers were fabricated by electrospinning with a 15 wt% m-aramid/DMAc solution, followed by either water or thermal treatment. The thermal stability and crystalline structure of the m-aramid nanofibers were investigated by thermogravimetry (TGA) and X-ray diffractometry (XRD), respectively. The effects of the water and thermal treatments on the dyeability of m-aramid nanofibers containing either pigment or dye were compared based on the K/S value and color difference. The results indicated that the use of dye is preferable to the use of pigment to improve the color depth of m-aramid nanofibers.