Seiji is a distinctive boys' name in United States, ranking #13797 in 2019 with 5 recorded births. The name reached its all-time peak in 2007 with 19 births ranking #4951. Since 1996, the popularity has decreased by 37.5%. In 2019, approximately 1 in every 358,672 boys born was named Seiji. FALLING Recent data shows the name is currently falling.