Rowley led the Peoples National Movement in the September 2015 general election, in which his party secured 23 out of 41 seats in the House of Representatives to form the government, defeating the previous Peoples Partnership coalition government. On 9 September 2015, Rowley was sworn in as Prime Minister of Trinidad and Tobago by President Anthony Carmona. 
He becomes the seventh Prime Minister of Trinidad and Tobago and the second Tobago-born Prime Minister. Rowley again led the Peoples National Movement to victory in the 10 August 2020 general election for a second term in government under his premiership. He was sworn in as Prime Minister of Trinidad and Tobago on 19 August by President Paula-Mae Weekes at the Presidents House in St. Anns after the opposition party asked for recounts to be done in marginal constituencies.
During his tenure, on 5 February 2022, the Trinidad and Tobago coast guard fired upon a vessel with Venezuelan migrants while attempting to stop it, killing a nine-month-old baby and injuring his mother. The coast guard claimed that the shots were fired "in self-defense". Rowley deemed the action "legal and appropriate"; the Trinidadian police and coast guard opened an investigation of the event.