Reinfeldt was hailed on social media after he spoke out strongly against immigration critics who claim Sweden is "collapsing".
The former leader of the Moderate party, who ruled Sweden in a centre-right coalition government from 2006-2014, became known across both sides of the political spectrum for his pro-immigration stance, famously urging Swedes to "open their hearts" in 2014.
But the public debate on Europe's refugee crisis has since changed and immigration is becoming an increasingly thorny topic in the Nordic country, which has tightened its asylum rules and stepped up border checks after taking in a record number of new arrivals last year.
However, addressing a charity gala last week, the ex-prime minister stood by his words and his comments went viral over the weekend.
"True vulnerability is to put your family on a boat which you don't know if it's going to make it across the sea. True vulnerability is to flee even if you don't know where you're going, if you will get there, if you will even survive. But this is what it is when the alternative is impossible to live with. Therefore, you have to escape. That is vulnerability," he said.
Reinfeldt gave the speech last Monday, before EU leaders struck a deal with Turkey designed to limit the inflow of refugees to the continent, but it did not grab headlines until over the weekend after it was shared by a civil rights lawyer on Facebook alongside the words, "the speech a prime minister should have given".
Sweden took in around 163,000 refugees in 2015 and has been struggling to provide schools and housing for all, with current centre-left prime minister Stefan Löfven battling declining support in the polls.
But Reinfeldt urged Swedes not to exaggerate the crisis.
"In our country we have now started using words to describe what Sweden is exposed to and I have understood that we're living in a collapse[d society]. Everything has stopped working. With those kinds of words we're there again – what do words mean in our time?"
"I have spent a few weeks meeting people and asking, in this country of collapse, how their Christmas holidays were. What was it like celebrating Christmas in a collapse? If Sweden is collapsing and nothing is working, what words do we have left to describe what is happening in Syria right now?"
Robert Hårdh, head of Swedish human rights group Civil Rights Defenders, criticized Swedish and European leaders in an interview with the Metro newspaper after he shared the video of the speech.
"Negative asylum policies being carried out within the EU are fuelling a strong counterforce that is extremely dangerous. We're lacking a leader who can take advantage of the strong, positive voices in society," he said, praising Reinfeldt's words.
By Monday the Facebook clip had been shared 1,024 times and was one of the most re-posted stories in Sweden. "Nice to hear this speech," commented one on the video. "What an enormous importance a person can have in politics," wrote another.
However, some critics slated the former leader, with one writing "perhaps that's why he's not prime minister any more", and another calling him a "traitor".
Reinfeldt, 50, who also served as president of the European Council in 2006, was last week hired by Bank of America Merrill Lynch as senior adviser in Europe, the Middle East and Africa.