Mehrtens, 32, has been appointed a Member of the New Zealand Order of Merit.
New Zealand's all-time record points-scorer retired from the All Blacks this year after 72 games in the famous jersey, scoring 967 points.
Mehrtens, who joined Harlequins in June, finished his career in New Zealand with a Super 12 victory for the Crusaders in May.
Former New Zealand Maori rugby coach Matt Te Pou becomes a member of the Order of Merit, as does ex-All Blacks captain and New Zealand Rugby Union president Tane Norton.
Norton, 63, played 61 matches, including 27 Tests, for the All Blacks and captained the side in the 3-1 series win against the 1977 British Lions.
He was NZRU president for two years, retiring this year, and is currently vice-president of the Canterbury Rugby Union and president of Christchurch's Linwood Rugby Club.
Former All Black and current Sport Waikato chief executive Matthew Cooper also received the Member of the New Zealand Order of Merit.
Cooper, 39, represented the All Blacks 18 times and played 124 games for Waikato, helping the club to three Ranfurly Shield wins.
He also played for the Highlanders and the Chiefs in the Super 12 before retiring in 1999.