In Alzheimer's disease (AD) research, the 5xFAD mouse model is commonly used as a heterozygote crossed with other genetic models to study AD pathology. We investigated whether the parental origin of the 5xFAD transgene affects plaque deposition. Using quantitative light-sheet microscopy, we found that paternal inheritance of the transgene led to a 2-fold higher plaque burden compared with maternal inheritance, a finding consistent across multiple 5xFAD colonies. This effect was not due to gestation in or rearing by 5xFAD females. Immunoblotting suggested that transgenic inheritance modulates transgenic protein expression, potentially due to genomic imprinting of the Thy1.2 promoter. Surprisingly, fewer than 20% of 5xFAD studies report breeding schemes, suggesting that this factor might confound previous findings. Our data highlight a significant determinant of plaque burden in 5xFAD mice and underscore the importance of reporting the parental origin of the transgene to improve scientific rigor and reproducibility in AD research.