[1] In December 2017, Seifert scored the fastest century in a domestic Twenty20 match in New Zealand, batting for Northern Districts against Auckland in the 2017–18 Super Smash.
[3] He was the leading run-scorer in the 2017–18 Plunket Shield season for Northern Districts, with 703 runs in nine matches.
[6][7] In October 2020, he replaced the injured Ali Khan in the Kolkata Knight Riders team in the 2020 Indian Premier League (IPL), but did not play a match during the competition.
[8] Seifert was retained in the Kolkata squad for the following season's IPL but did not play before the suspension of the league in May during the COVID-19 pandemic.
[16] In August 2021, Seifert was named in New Zealand's squad for the 2021 ICC Men's T20 World Cup.