Seiji is a distinctive boys' name in United States, ranking #6700 in 2008 with 13 recorded births. The name reached its all-time peak in 2007 with 19 births ranking #4951. Since 1996, the popularity has increased by 62.5%. In 2008, approximately 1 in every 156,919 boys born was named Seiji. FALLING Recent data shows the name is currently falling.