Anthony Seibold was born in Rockhampton, Queensland, Australia, and is of German descent from his grandfather, and predominantly Irish and English from his paternal grandmother's side.

[3] As a player, Seibold had stints in the lower grades at the Brisbane Broncos (1992–1995) and in the National Rugby League with the Canberra Raiders (1997–1998).

Seibold played for the Ipswich Jets in the 2002 Queensland Cup Grand Final before returning to the UK.

[citation needed] In 2006, he moved to Wales where he was assistant coach at Celtic Crusaders between 2006 and 2009, playing in the first season.

[citation needed] After working as an assistant coach at the Melbourne Storm under Craig Bellamy, Seibold was recruited to join the Manly Warringah Sea Eagles.

[4] In his first year as Souths coach, Seibold guided the club to a third-placed finish at the end of the regular season.

[5] In November 2018, Seibold angrily spoke to the media about a possible switch with Brisbane coach Wayne Bennett.

It’s not acceptable and it’s not fair … He’s (Wayne Bennett) been ringing up the Souths boys but then tells his press conference he hasn’t spoken to anyone.

Between rounds 16 and 24, Brisbane only lost 2 out of 8 games and qualified for the finals with a 17–16 victory over the Parramatta Eels at Suncorp Stadium.

[10][11][12] Brisbane started the 2020 NRL season with two wins in a row against North Queensland and Seibold's former team, South Sydney.

Under Seibold, 2020 was the worst year in Brisbane's history with only 3 wins from 20 matches and a points differential of −356 resulting in the club's first wooden spoon.

In his first season in charge of Manly, he guided the club to win only four of the opening ten, being on the receiving end of some big score lines.