<p>Neuropeptide Y (NPY) has emerged as a key modulator of stress resilience, primarily through activation of the Y1 receptor (Y1R). We previously demonstrated that intranasal delivery of the Y1R-selective analog D[His²⁶]NPY at the time of trauma induced by Single Prolonged Stress (SPS), a validated rodent model for post-traumatic stress disorder (PTSD), effectively prevented stress-induced behavioral impairments in male rats. D[His²⁶]NPY was more effective than either intranasal administration of native NPY or the Y1R agonist [Leu³¹Pro³⁴]NPY. In females, who are more susceptible to stress-related anxiety disorders and PTSD, native NPY has shown limited efficacy. Here, we investigated: (1) efficacy of intranasal D[His²⁶]NPY in female rats; (2) time-dependence of intranasal administration of D[His²⁶]NPY effectiveness for males, in preventing or reversing behavioral impairments. Our results revealed that in female rats, D[His²⁶]NPY produced robust anxiolytic effects at lower doses than native NPY. In male rats, intranasal D[His²⁶]NPY administered at the time of trauma, or 1&#xa0;day before, averted the development of SPS-induced anxiety and social interaction deficits. Even when given two days prior to the traumatic stress intranasal D[His²⁶]NPY was partiallly effective. However, in contrast to native NPY, D[His²⁶]NPY failed to reverse the established behavioral impairments, when administered two weeks after SPS. These findings suggest that despite sex-specific differences, nose to brain delivery of the Y1R agonist D[His²⁶]NPY could be especially useful as a prophylactic treatment to prevent long-term adverse harmful effects of traumatic stress in both males and females.</p>