Protein/peptide aggregation-induced cell death is the culprit of many neurodegenerative diseases. Many peptide drugs were designed to inhibit protein/peptide aggregation. However, the brain penetration rate is a key issue in determining the efficacy of the peptide drugs in the brain. The nose-to-brain drug delivery is a potential administration route to bypass the blood-brain barrier and to avoid peptide degradation that possibly occurred in other administrative routes. Here, the temporal and spatial distribution of a radiolabeled anti-amyloid peptide, that could reduce the amyloid load and attenuate the cognitive decline in AD transgenic mice via intranasal administration, was examined by the SPECT/CT scan. The brain uptake rate was 0.73–1.78%ID/g tissue. The biological half-life of the peptide in the brain was 10.2 ± 0.8 h.