State Assemblyman

He was the political secretary to the Menteri Besar of Selangor Abdul Khalid Ibrahim from March 2008 to June 2010.

Nik Nazmi was appointed as Communications Director of PKR in August 2010.

In the 2013 Malaysian general election Nik Nazmi defended his Seri Setia state seat. He defeated Abdul Halim Samad of Barisan Nasional with a majority of 4,663 votes.

He was then elected as Deputy Speaker of the Selangor State Legislative Assembly. During this time he inaugurated the Selangor Youth ADUN Program (Program ADUN Muda Selangor) that allowed students the experience of being legislators in the State Assembly.

Nik Nazmi is the first person to be charged under the Peaceful Assembly Act 2012 for failing to give police a 10 days' notice before holding the post-election Kelana Jaya Blackout 505 rally. If convicted under section 9(5) of the same Act, Nik Nazmi could be fined up to RM10,000, which could see the Seri Setia state assemblyman losing his seat.^[7] The rally is to protest against the election results and demand a free and fair election.

In a landmark judgment in April 2014 following Nik Nazmi's challenge on the constitutionality of the Act, the Court of Appeal unanimously ruled that it is unconstitutional to criminalise fundamental freedoms and acquitted Nik Nazmi.

PKR Youth Chief

In the Parti Keadilan Rakyat party elections in 2014, he was elected as the Leader of the Youth Wing.

Nazmi was appointed as the State Executive Councillor in charge of Education, Human Capital Development, Science, Technology and Innovation in 2014.

Member of Parliament

On 9 May 2018, Nik Nazmi moved to Contest the Setiawangsa Parliamentary Constituency and subsequently won the seat with a 14,372 majority.

In the 2018 PKR party elections, he was elected as a member of the Central Leadership Council and appointed as Chief Organising Secretary of the party.

Four years later, he was elected as a Vice President of the PKR.

In the 15th General Election 2022 Malaysian general election, Nik Nazmi successfully retain the seat of Setiawangsa with a 12,614 vote majority.

Minister of Natural Resources, Environment and Climate Change

Soon after the formation of the unity government led by Anwar Ibrahim, Nik Nazmi was subsequently appointed as the new Minister of Natural Resources, Environment and Climate Change. At the age of 40, he is the second youngest full cabinet member serving in Anwar Ibrahim cabinet, with the youngest member being UPKO President Ewon Benedick

This Ministry is a combination of two Ministries previously: the Ministry of Energy and Natural Resources as well as Ministry of Environment and Water. One of the early landmark of his reign as minister was the introduction of a climate policy that not only focuses on climate mitigation but also climate adaptation and resilience. Under his stewardship, Malaysia also remove the blanket subsidy on electric usage.

Being a son to proud Kelantanese parents, one of Nik Nazmi's earliest pledges was to resolve the water issue in Kelantan once and for all. Despite Nik Nazmi's party People's Justice Party (Malaysia) having no MPs and state assemblyman in the state.

In December 2022, Nik Nazmi announce that the federal government led by his ministry will carry out 40 projects to construct flood barriers, walls and environment-friendly drainage systems in efforts to mitigate the risk of flooding in the east coast states of Kelantan and Terengganu. He added that "The ministry is also implementing a few other actions, including the maintenance of the drainage system through the Integrated Flood Management Approach and the development of necessary infrastructure. For example, upgrading the flood management system for the coast and main rivers as well as improving the level of safety in the design infrastructure for drainage and the coast."

In July 2023, Nik Nazmi along with the Economic Minister Rafizi Ramli launched the National Energy Transition Roadmap (NETR), which contribute to a fair and equitable energy transition and boost the growth of the country’s renewable energy industry, especially renewable energy.

In August 2023 in his capacity as Minister of Natural Resources, Environment and Climate Change, Nik Nazmi announced the cancellation of the Tioman Island airport project. He cited that his ministry has taken note of concerns voiced over the reclamation of land as part of the airport's development, which will take place in protected marine areas, causing the destruction of coral reefs and loss of habitat to hundreds of species of marine life, which are the main attractions of Tioman island.

In October 2023, Nik Nazmi by way of written reply to parliamentary questions clarify on the details of the latest approved Power Development Plan (PDP). In his written reply, he states that Under Malaysia’s latest approved electricity generation plan, 37.81% of the nation’s installed electricity capacity in 2030 will be powered by renewable sources. the transition from coal-based generation sources to renewable energy is in line with the government’s net zero commitment under the Paris Agreement, as well as its own target of increasing RE’s share of electricity capacity to 70% by 2050.

This increase in RE capacity will allow excess capacity to be exported cross-border with neighbouring countries in the region based on a mechanism that will be set by the government, further fulfilling the desire to realise the Asean Power Grid initiative. The planning of electricity supply through the PDP emphasises the balance of the energy trilemma, namely energy security, sustainability and affordability

In November sitting of the Malaysian Parliament, Nik Nazmi replied in response to a question stated in Parliament that "The government intends to review the 1962 water agreement with Singapore because of "certain issues" with aspects of the agreement." He add-on that "We believe it is important to review the water agreement because we believe there are 'a few problems' within some aspects, and we want to review it to find the best solution." He further added that there are plans being made by the federal government to enhance the capacity of the Johor River.

Minister of Natural Resources and Sustainability

On the 12th of December 2023, Prime Minister Anwar Ibrahim announced a cabinet reshuffle where the original natural resources, environment and climate change was split into 2. Nik Nazmi retains partial of his original portfolio. When asked by the media after attending Energy Commission's "A Decade of Energy Efficiency Challenge: Cultivating Energy Efficiency Culture Among School Students", Nik Nazmi stated that the division of NRECC into two ministries allows the government to address climate change and environmental sustainability more inclusively and justly. He further added that the changes made to NRECC, by Prime Minister Datuk Seri Anwar Ibrahim during the Cabinet reshuffle, align with the global and domestic situation's strategic needs and demands.