Finn and Anthony, aged 12 and 13, were on their way home after playing Yu-Gi-Oh with friends on Saturday afternoon when they spotted the men by an U-Bahn station, near the city's southern gate Sendlinger Tor.
The men seemed listless and some were lying on the ground.
"They didn't look healthy," Finn told Münchner Abendzeitung.
"One of the men had tried to wake his friend up, but couldn't. He then disappeared towards the tube station."
Yet knowing that drug addicts and drunkards often frequent the area, the two boys said they were wary of approaching the men - and shortly before, a witness had seen the group drinking beer and smoking what seemed to be synthetic marijuana.
Yet while hoards of people walked past, nobody seemed concerned the boys said.
"They could see that the men were in trouble," said Anthony. "But nobody wanted to stop and help."
At Finn's suggestion, the boys called for an ambulance – and a few minutes later, four vehicles arrived.
Finn und Anthony, 12 und 13 Jahre alt, retten einem Mann am Sendlinger Tor das Leben - alle anderen schauen weg http://t.co/eKcghC8XjM— SZ München (@SZ_Muenchen) July 19, 2015
Paramedics had to resuscitate two of the men, aged 37 and 40, while a third member of the group also lost consciousness, reports the Abendzeitung.
All three men were rushed to hospital.
"I just wish that the adults who walked past had helped the men, instead of just looking away," said Finn.
Yet he and Anthony couldn't believe what happened after the ambulances arrived.
"As the paramedics were treating the men, people suddenly started to stop and take notice," said Finn. "Some even got out their phones and started to take videos."
Carsten Neubert, spokesperson for Munich Police, told The Local that the group had fallen foul of "a mix of alcohol consumption and drug use".
He confirmed that paramedics had had to use resuscitation techniques before taking the men to hospital – but that all men had been treated and had survived the incident.
Police said they want to nominate the boys for a Life Saver's Award for their efforts.
"We have two separate emergency numbers – 110 for the police and 112 for ambulance and fire services – and the boys did the right thing by calling 112.
"Their actions saved a man's life," he continued, saying that anyone who finds themselves in a similar situation should follow the boys' lead.
Reporting by Hannah Butler.