Seiji is a distinctive boys' name in United States, ranking #7024 in 2010 with 12 recorded births. The name reached its all-time peak in 2007 with 19 births ranking #4951. Since 1996, the popularity has increased by 50.0%. In 2010, approximately 1 in every 159,868 boys born was named Seiji. FALLING Recent data shows the name is currently falling.