Osarobo 'John' Izekor (36) and his 29-year-old wife Precious Izekor will also have to pay their victim £10,000 in compensation.
The husband and wife, with an address at Ashmount Gardens in Lisburn, admitted that on dates between September 1, 2016 and September 30, 2017 they ‘required another person to perform forced or compulsory labour’.
Whilst the victim was forced to carry out domestic duties, a majority of the criminality by the Izekors was unpaid childcare.
The case, which was heard at Belfast Crown Court, is one of the first prosecutions under the Human Trafficking and Exploitation Act (NI) 2015.
The couple admitted keeping the Nigerian woman as a domestic slave in their then Castlereagh Place home in Belfast for a ten-month period.
Crown barrister Charles MacCreanor said the woman - who could not read or write - arrived in Northern Ireland in 2011 and worked as a nanny for a five-year period.
When her employer returned to Nigeria in Autumn 2016, she moved into Castlereagh Place and was told money would be sent back to her family for any work she undertook.
During the ten-month period of offending, the woman had her own room and was given food and clothes - but was not paid any money.
In addition, the Izekors had possession of her passport and other documents, which she didn't have access to.
Mr MacCreanor said that whilst living with the Izekors, the woman was in contact with a relative of John's, who expressed a desire for her to return to Nigeria so they could get married.
This relative asked the woman about her documentation and visa status, and when she raised this issue with Precious, an argument ensued.
Despite her request for her documents, they were not handed over to the woman and the argument led to a "deterioration of relations".
Following this, the woman tried to look for her passport and other documents when Precious Izekor was out. A few days later, she left the Izekors and went to stay with a friend.
This friend, the court heard, was concerned for the woman, felt she was being exploited and accompanied her to the Home Office.
When a Home Office official called at the Izekors' home, Precious was asked about the woman, and denied knowing her.
An investigation was launched which resulted in the involvement of the PSNI and the subsequent arrests of both John and Precious Izekor.
During his police interview, John Izekor initially denied any wrong-doing and made the case they were letting the women stay in their home and were helping her.
In her interview, Precious told officers the woman was a family friend and was never asked to do any form of work or labour.
Mr MacCreanor said there were text messages between the husband and wife which indicated the control they had over the woman whilst she was living with them.
He also said that she spoke to police about her ordeal, the woman said she felt isolated and alone whilst living with the couple.
Defence barrister Barry Gibson, representing John Ikezor, said that following his arrest his client spent three months on remand.
He also spoke of Izekor's university education, extensive work history and his clear criminal record.
Precious Izekor's barrister Gavan Duffy QC revealed there was a former good relationship between the two women, and said there was a complete lack of violence or physical assault.
After listening to submissions from both the Crown and defence, Judge Richard Greene QC spoke of the complexities of the case and said he wanted to consider several issues before passing sentence.
After being told that the Izekors had previously lodged £10,000 to the court to act as a surety for bail, the judge ordered that this money be paid to the woman they kept as a domestic slave.
Judge Greene told the couple the charge they pleaded guilty to was "an extremely serious offence" and released them on continuing bail ahead of sentencing, which is set to take place on June 27.