[23] It was founded in 1989 by Basdeo Panday, a Trinidadian lawyer, economist, trade unionist, and actor after a split in the ruling National Alliance for Reconstruction (NAR).

The UNC's Political Leader, Kamla Persad-Bissessar, was sworn in as the first female Prime Minister of Trinidad and Tobago.

It won a 14th seat in a by-election and gained another in 1995 when Ralph Maraj defected from the ruling People's National Movement (PNM) party.

In 1995, the UNC lost one seat when Hulsie Bhaggan, member of parliament for Chaguanas, left the party to form the Movement for Unity and Progress (MUP).

In exchange for his support, NAR Political Leader A. N. R. Robinson was first appointed Minister Extraordinaire and then elected President in 1997.

On 31 May 2005, Panday, his wife Oma, former UNC MP Carlos John, and party financier Ishwar Galbaransingh were arrested for bribery.

On 2 October, Panday's slate won 12 of the posts including two of the three deputy leader positions and, after a recount, the vice-chairmanship.

Gerald Yetming, MP for St. Joseph, joined the Opposition backbenches in protest of Panday's refusal to relinquish his position.

On 24 April, Panday was convicted of fraud for failing to disclose a bank account under the rules of the Integrity Act.

On 25 April, Panday's appointment as Opposition Leader was revoked by President George Maxwell Richards.

Persad-Bissessar was appointed Opposition Leader the following day but stated that she would step aside should Panday's appeal prove successful.

Amidst the infighting, Panday returned to active politics in August 2006 and attempted to publicly broker a reconciliation between the two factions.

Dookeran, who was seen as the legitimate Political Leader of the UNC, was unable to exercise the full powers granted to him in the Party's Constitution.

However, Dookeran's call for internal change within the UNC was negatively viewed by some of the party's 'old guards' who felt their position threatened.

Panday loyalists organised themselves into a five-member Leadership Council, composed of the three Deputy Leaders (Persad-Bissessar, Wade Mark, and Jack Warner), the Party CEO Tim Gopeesingh, and the newly returned Maharaj.

On 10 September at a large rally, Dookeran announced his resignation as UNC Political Leader and the formation of a new party: the Congress of the People.

[33] In the internal election, she won 13,932 votes compared to 1,359 for Basdeo Panday and 1,072 for Ramesh Maharaj and became the first female leader of a major political party in Trinidad and Tobago.

Based on a campaign of change against the PNM, the UNC was successful in the 2010 general election, and Persad-Bissessar was appointed as the first-ever female Prime Minister of Trinidad and Tobago.

The Movement for Social Justice, which did not win any seats in the election, left the coalition due to discontent with the running of the government.

[34] Controversy arose when ballots in favor of Roodal Moonilal were found near a river and at the back of a school used as a polling station.

According to the election authorities, three of the UNC's candidates were found ineligible or withdrew themselves before polling day, resulting in a walkover victory for the PNM in one district.

[36] In the 2017 internal elections Kamla Persad-Bissessar won virtually all of the votes to continue as political leader of the party against Chanda Bhaggan and Christine Newallo Hosein.

The UNC's campaign was based on the incumbent PNM government's mishandling of the COVID-19 pandemic, not doing more to control the Venezuelan refugee crisis and having a failing economy.

[41] The party also faced questions of corruption amid a police investigation that involved members of the UNC.

[48][49][50] Focus on the leadership election occurred when Anita Haynes, Public Relations Officer of the UNC, was questioned by reporters on whether or not the Opposition Leader Kamla Persad-Bissessar would resign.

[51][52][53][54] Devant Maharaj was a leading figure in calling for Kamla Persad-Bissessar to step down as political leader.

He also stated the party needs to determine the reason for the low voter turnout then they need to "inspire their ground troops" to win the next general election.

[59] Founder of the party, Basdeo Panday, commented before the election that the UNC had no future under the leadership of Kamla Persad-Bissessar nor Vassant Bharath and would eventually die out.