New Green MP Ricardo Menéndez March is completing a two-week stint in a managed isolation hotel after travelling to Mexico over summer.
The new list MP, who grew up in Tijuana, returned to his home country for "serious personal family matters" in mid-December, a party spokesperson said.
Menéndez March left the country on 13 December and returned on 1 February. He is expected to leave managed isolation (MIQ) next week.
A Green Party spokesperson said Menéndez March had "followed the appropriate processes to return" to the country.
"We look forward to seeing him upon his return."
The travel goes against the official advice on the government's SafeTravel website which urges all New Zealanders to remain in the country.
"We currently advise that all New Zealanders do not travel overseas at this time due to the outbreak of Covid-19, associated health risks and widespread travel restrictions," the Ministry of Foreign Affairs (MFAT) website reads.
Questions about Menéndez March's whereabouts were raised on Tuesday after he missed the first day of Parliament for the year.
Menéndez March applied for an emergency MIQ spot to re-enter New Zealand earlier, but the request was declined by the Ministry of Business Innovation and Employment (MBIE).
A spokesperson for Covid-19 Minister Chris Hipkins said he had been notified of the request under the 'no surprises' policy but had no say over the decision.
MBIE declined to comment on the case, citing "privacy reasons".
The government-run MIQ system has come under increasing strain in recent months with New Zealanders abroad struggling to secure spots in order to return home.
New regulations came into force in August, meaning anyone who left the country and then later returned is charged $3100 for the MIQ stay.
RNZ has approached Menéndez March for comment.