Seiji is a distinctive boys' name in United States, ranking #5635 in 2011 with 16 recorded births. The name reached its all-time peak in 2007 with 19 births ranking #4951. Since 1996, the popularity has increased by 100.0%. In 2011, approximately 1 in every 118,687 boys born was named Seiji. FALLING Recent data shows the name is currently falling.