"It's important for me to hear what people really think. If there's one place where people say what they think, it's in the taxi," he said in a video posted on Facebook, Twitter and YouTube.
The video was released while campaigning was in full swing for the September 9 general election, which Stoltenberg's ruling centre-left coalition appears likely to lose, according to the latest opinion polls.
Stoltenberg wore an Oslo Taxi uniform - complete with a badge - one afternoon in June and picked up passengers in a black Mercedes in the Norwegian capital.
A hidden camera fitted in the cab recorded reactions from the passengers, including one who remarked: "From this angle, he really looks like the prime minister."
An elderly woman who also recognised Stoltenberg urged him to do something about "the salaries of bosses", complaining that "they should not make millions like that".
Beyond revelations from the clients, Stoltenberg himself had one to give away, admitting to a passenger who recognised him that he had not driven in eight years.
Asked by tabloid Verdens Gang if he would like to be a taxi driver if he lost the elections, Stoltenberg said: "I think that the country and Norwegian taxi passengers are better served if I were a prime minister and not a taxi driver."
According to the tabloid, the passengers did not have to pay for their journeys.
