[4] Berejiklian became a member of the New South Wales Legislative Assembly after winning the electoral district of Willoughby in the 2003 state election.

However, Berejiklian easily saw off a rematch with Reilly after picking up a healthy swing of 14.5 points, enough to revert Willoughby to its traditional status as a comfortably safe Liberal seat.

[30] Berejiklian restructured the railway system from July 2013 with RailCorp and its CityRail and CountryLink brands replaced by Sydney Trains and NSW TrainLink.

[31] Notable projects include the extension of the Inner West Light Rail from Lilyfield to Dulwich Hill;[32] the introduction of the Opal card;[33][34] commencement of construction of the Sydney Metro Northwest.

[36][37] Despite receiving the support of Barry O'Farrell to succeed him, and despite having the numbers to win the premiership in a partyroom ballot, Berejiklian chose not to run for the leadership of the New South Wales Liberal Party.

[24][40] Berejiklian was appointed as Treasurer of New South Wales and Minister for Industrial Relations following a cabinet reshuffle announced on 1 April 2015 by Premier Baird, after the 2015 state election.

In October 2018, Berejiklian permitted advertising for The Everest stakes to be projected onto the sails of the Sydney Opera House (a move spearheaded by radio broadcaster Alan Jones), drawing widespread condemnation and criticism from many in the community, with a poll declaring that 80% of respondents opposed this decision.

Three of these parliamentarians, MP Tanya Davies and Legislative Council members Matthew Mason-Cox and Lou Amato, "expressed dissatisfaction with Berejiklian's handling of the bill".

They had repeatedly asked Berejiklian to "intervene to stop the "fast-tracking" of the bill and establish a joint select committee into the legislation reform".

[58][59] In October 2020, as part of her evidence to an Independent Commission Against Corruption (ICAC) inquiry, Berejiklian admitted that she had been in a "close personal relationship" with Daryl Maguire from 2015 until August 2020.

Maguire had been a fellow Liberal MP until a previous inquiry had heard that he had sought inappropriate payments, leading to his resignation in 2018.

[67] The decision to not prevent residents of Sydney regional and interstate travel resulted in the spread of COVID-19 to other states, including the Northern Territory, Western Australia and Queensland.

[74] The discrepancy in enforcement between different suburbs in the LGAs of concern attracted controversy, with some suggesting the restrictions were unrelated to the levels of transmission and rather, population demographics.

[75][76][77][78][79] Berejiklian also faced criticism when she stopped attending daily press briefings as COVID-19 cases, hospitalisations and deaths were predicted to peak.

[80] On 1 October 2021, New South Wales' ICAC announced an investigation into whether Berejiklian breached public trust or encouraged corrupt behaviour during her relationship with Daryl Maguire.

She later announced she would be "spending her last days in office addressing local concerns" before officially resigning as member of the Legislative Assembly on 30 December 2021.

[90] In December 2021, after speculation that she might contest in the 2022 federal election, Berejiklian confirmed that she would instead work in the private sector and looked forward to "a much less public life".

[93] In July 2024, the Court of Appeal rejected Berejiklian's challenge and upheld ICAC's original ruling that her behaviour was corrupt.

[100] Federal Opposition Leader Peter Dutton defended Gladys Berejiklian, saying she was "not corrupt" but was engaged in a bad relationship.

[104] In February 2022, Berejiklian was appointed to the executive board of telecommunications company Optus, in the newly created role of Managing Director, Enterprise, Business and Institutional.

In September 2018, Sydney electronic music duo Twisted Melodiez in collaboration with Melbourne-based N3bula released a song named "Shut this Down", which remixed comments made by Berejikian in a press conference that year in which she vowed to ban future iterations of Defqon.1 in New South Wales as a result of a number of drug-related deaths at the festival, as well as categorically ruling out implementing pill testing in New South Wales.