The first contractor admitted two corruption charges on September 6.
The SFO said both men were Australian citizens. Both currently have name suppression.
Between late 2013 and mid-2017, the contractor who paid the kickbacks received contracts of more than $20m of work on the recommendation of the contractor who received the kickbacks.
“The two contractors had a prior relationship before they worked for the New Zealand-based company,” the SFO added.
“The second guilty plea is a key milestone in the SFO’s prosecution of this case and illustrates the severe harm that arises when someone abuses their position of trust for personal gain,” SFO director Karen Chang said.
“Participating in schemes that involve bribery and corruption undermines the integrity of New Zealand’s business sector but also erodes public confidence in fair business practices.”
The two men will next appear in court on December 4.
The first contractor was arraigned on two charges last month but another 30 charges were withdrawn.
He was allowed to return to Australia on bail but Justice Simon Moore told him to return to Auckland for his next hearing.
