The utilization of by-products from the food industry is becoming increasingly important. Walnut flour (WF) is a by-product of walnut cold-pressed oil extraction that is rich in healthy lipids (55.7%), proteins (24.6%), dietary fiber (9.4%), minerals, and bioactive compounds. Furthermore, the staling of gluten-free (GF) products represents a serious problem since it usually occurs faster than in their gluten-containing analogues. Considering that previous studies showed that WF positively affects the quality of fresh GF cakes and that WF has high lipid content, it is expected to modify staling positively. Thus, the study aims to investigate the effect of WF addition (0%, 10%, 15% and 20%) on the technological quality and the fatty acid profile of GF cakes during storage. The GF cakes underwent the typical staling changes: loss of moisture, crumb hardening, and crust softening, among others. However, WF led to an attenuation of these phenomena. Also, as the addition of WF increased, a reduction in starch retrogradation and an increase in the amylose-lipid complex content were observed. Besides, the fatty acid profile remained unchanged during storage. These results showed the suitability of WF as an ingredient for developing GF cakes that retain better technological quality during storage.