On 4 February 2025, after the Centre Party withdrew from the Støre Cabinet, Stoltenberg returned to Norwegian politics by being appointed as the new Minister of Finance, succeeding Trygve Slagsvold Vedum.

Following heavy bombing raids against the North Vietnamese port city of Hai Phong at the end of the Vietnam War, he participated in protest rallies targeting the United States Embassy in Oslo.

Stoltenberg's first tenure as Prime Minister (2000–2001) was controversial within his own party, being responsible for reforms and modernisation of the welfare state that included partly privatising several key state-owned services and corporations.

"[15] Some analysts[citation needed] have pointed out that one of the causes for their loss was that with only one year in power until the next election, more time was spent initiating or trying to start reforms than telling the people why they had to be done.

Since the government's formation, key political issues such as Norwegian military participation in the war in Afghanistan, petroleum activities in the Barents Sea, LGBT rights, immigration and the quality of standard education were greatly debated by the public.

Following Stoltenberg's re-election in 2009, he worked on the Norwegian response to the ongoing global recession and championed for environmentalist policies through private and corporate taxation.

[27] On 22 July 2011, a far-right extremist committed two attacks: a bomb went off in Oslo outside the government building which houses the prime minister's office, killing eight people while wounding others.

After Erna Solberg formed her cabinet, Stoltenberg returned to the Parliament as leader of the opposition, and a member of the Standing Committee on Foreign Affairs and Defence.

This was among other arenas done through the International Monetary Fund (IMF) and a meeting in Chile 27–29 March 2009 where social democratic leaders from around the world met at a Progressive Governance Conference, just prior to the first G20 summit on the financial crisis.

A special emergency meeting of the European Social Democratic Forum (PES) was gathered in Oslo in May 2011, on an initiative from Stoltenberg and the think tank Policy Network.

[50] Partnering with tropical countries to preserve more of their rainforest to bind carbon dioxide (CO2) in order to reduce greenhouse gas emissions was a policy of the Stoltenberg government.

During the meeting there he met with Secretary-General Ban Ki-moon as well as UN Framework Convention director Christiana Figueres and both Achim Steiner and Helen Clark of the United Nations Development Programme.

[54] Stoltenberg was one of the key driving forces behind the initiative, and has stressed that this is an important contribution to save 9 million children from dying of the most common childhood illnesses.

[63][64] Norway was a founding member of NATO in 1949, and Stoltenberg is the first Norwegian to serve as secretary-general, although former Conservative Party Prime Minister Kåre Willoch was considered a strong candidate in 1988.

[73] In 2016, Stoltenberg stated that the NATO strongly supported "the UN-led political process to find a solution" to the dispute over the northern part of Cyprus, which has been under illegal occupation since the Turkish invasion of 1974.

[83] At the July 2018 Brussels Summit, the Alliance reconfirmed its commitment to preserving the credibility, coherence and resilience of the deterrence and defense posture, including by increasing its responsiveness, heightening readiness and improving reinforcement.

[90] Stoltenberg "strongly condemned" the 2019 Abqaiq–Khurais attack on key Saudi Arabia's oil facilities and accused Iran of "supporting different terrorist groups and being responsible for destabilising the whole region.

Stoltenberg said, following a meeting on 6 January, "all members of the Atlantic alliance stood behind the United States in the Middle East" and that "Iran must refrain from further violence and provocations.

Amongst the topics he chose to address were Donald Trump's call for the European allies to contribute more funds to the common military good, the situation in Afghanistan which he promised not to leave, and the desire of Russia to reimagine the world in terms of the spheres of influence of the post-war years of the 20th century.

In a thinly-veiled reference to Chinese leadership in the 5G telecoms sector, he said that "Keeping our societies open, free and resilient must be part of our response... We should not be tempted to trade short term economic benefits for longer-term challenges to our security.

[100] In October 2020, Stoltenberg called for an immediate end to the fighting over the breakaway Nagorno-Karabakh region, an enclave that belongs to Azerbaijan under international law but is populated and governed by ethnic Armenians.

[114][115][116] He said that "In a dialogue with the United States and its allies, we will insist on working out specific agreements that would exclude any further NATO moves eastward and the deployment of weapons systems that threaten us in close vicinity to Russian territory.

On 19 February at the Munich Security Conference Stoltenberg remarked that despite NATO's "strong diplomatic efforts to find a political solution [to the Ukrainian crisis]... we have seen no sign of withdrawal or de-escalation so far.

[134] While most current NATO members responded positively to the applications, Turkish president Recep Tayyip Erdoğan voiced his opposition, accusing both Finland and Sweden of tolerating Kurdish militant groups PKK and the YPG, which Turkey classifies as terrorist organizations,[135] and followers of Fethullah Gülen, whom Turkey accuses of orchestrating a failed 2016 Turkish coup d'état attempt.

"[145] He said that President Putin and the decision makers in Moscow are the only ones responsible for the Russo-Ukrainian War and it is necessary for NATO member countries to continue providing military aid to Ukraine.

[155] Responding to Stoltenberg's statement, Italian Defence Minister Guido Crosetto stated that it is "wrong to increase tension" in an already "dramatic" situation and emphasised the need to "leave open the possibility of negotiating an immediate truce and initiating peace talks in the coming months.

[162] On 18 June, it was announced Hungary and Slovakia had agreed to allow outgoing Dutch Prime Minister Mark Rutte to succeed Stoltenberg as Secretary General.

[169] His nomination was controversial prior to being officially announced, due to his links to the Labour Party, friendship with Prime Minister Jonas Gahr Støre and concerns for the independence of the central bank.

[176] On November 8, 2024, Stoltenberg was appointed Chairman of the Steering Committee of the Bilderberg Group, an annual private conference attended by political leaders, business executives, academics, and media representatives.

His musical choices included "Hungry Heart", sung by Bruce Springsteen; "So Long, Marianne", by Leonard Cohen; and "No Harm", by the duo Smerz, one of whom is his daughter Catharina.