"Sweden will not remain passive if a disaster or an attack would hit another EU country or a Nordic nation. We expect these countries to act the same way if Sweden is affected," Wallström reiterated to parliament as she presented her foreign policy targets for 2016.
Despite traditionally pushing a policy of military non-alignment, Sweden's ruling centre-left Social Democrat-Green government has been moving closer to Nato in the past year, amid growing fear of what is perceived as an increasingly aggressive Russia.
But opposition politicians hoping for a U-turn on Nato membership were left disappointed on Wednesday, and hit out at Wallström in the debate following her speech.
"What makes it so difficult to even discuss it? It would increase Sweden's security," asked Karin Engström representing the Moderates, the biggest centre-right party in parliament.
Members of the Centre Party, its colleague in the right-wing Alliance, questioned how Sweden's decision not to join the military organization contributes to security in Europe.
"We could recently celebrate 200 years of peace and that's no coincidence. It's the result of wise policies and freedom from alliances," countered Wallström.
In her speech, the outspoken minister also argued that in light of the refugee crisis, a stronger EU was ever-more important, addressing directly the UK's upcoming referendum on exiting the union.
"Internal division must be countered. It is vital that Great Britain remains in the union."
INTERVIEW: Wallström speaks to The Local about Brexit
She also addressed Sweden's candidacy for a place on the UN Security Council in 2017-2018, saying it would not stray from its feminist foreign policy to protect human rights.
Sweden will appoint a special 'human rights ambassador' and a 'disarmament ambassador' to campaign on human rights and non-proliferation, she said.
Wallström went on to urge other EU countries to "take their responsibility" in accepting a larger share of refugees fleeing wars in the Middle East and Africa, saying: "We can't have a situation where some countries buy blankets and others invest in barbed wire."
Sweden took in more than 163,000 asylum seekers last year, the most per capita in Europe, but it has been struggling to provide accommodation for the record-influx.
In a separate move on Wednesday, Prime Minister Stefan Löfven tasked his Labour Minister Ylva Johansson with overseeing integration for new arrivals in the country.
"We face very serious challenges and it's important that the state is as effective as possible and that all pieces of the puzzle fall into place. That's my mission," said Johansson.