The commissioner for happiness and couples' fulfilment is the brainchild of Rochas Okorocha, governor of the southeastern state of Imo.
Okorocha, who was previously widely criticised for using public funds to erect statues of prominent African leaders, on Monday appointed his sister to the post.
Ogechi Ololo now takes up the first such portfolio in Nigeria. She previously served as Okorocha's deputy chief of staff and special adviser on domestic matters, in charge of Christmas decorations.
The governor's spokesman, Sam Onwuemeodo, could not provide exact details of Ololo's responsibilities when contacted by AFP Tuesday, but said: "There is nothing unusual about the appointment".
"The governor is a man of ideas, always introducing new things to governance."
The commissioner's job "is an innovation that should be copied by other governors," he added. He "wants to always make the people happy. That's why he has created a ministry for that purpose."
The remote Himalayan kingdom of Bhutan is known for measuring its success by Gross National Happiness rather than Gross Domestic Product.
Criteria taken into account include psychological well-being, health, education, vitality in the community and the living standards enjoyed by the population.
Okorocha, a leading member in President Muhammadu Buhari's All Progressives Congress party, is one of Nigeria's best-known but also controversial state governors.
He has been accused of appointing family members and cronies to government offices without regard to the state's lean finances, including naming his son-in-law as chief of staff.
In recent months he has honoured Liberia's outgoing President Ellen Johnson Sirleaf and South Africa's Jacob Zuma with statues in the state.
Zuma's statue was reported to have cost 520 million naira ($1.4 million, 1.2 million euros).
Okorocha was criticised for the expense as public sector workers in Imo were owed several months' salary.
He has also been criticised for spending millions of naira to put up a Christmas tree reputed to be one of the biggest in the world.
