Speaking on TV, Maria Zakharova said Jews had told her they donated both to Mr Trump and Hillary Clinton.
She joked that American Jews were the best guide to US politics.
The diplomat's remarks caused shock. Anti-US propagandists in the last century peddled an idea that rich New York Jews controlled US politics.
Ms Zakharova was speaking on a chat show on Russian state TV at the weekend but her comments drew more attention after being picked up by media outlets on Thursday.
She said she had visited New York with an official Russian delegation at the time of the last UN General Assembly, in September.
"I have a lot of friends and acquaintances there, of course I was interested to find out: how are the elections going, what are the American people's expectations?" she said.
"If you want to know what will happen in America, who do you need to talk to? You have to talk to the Jews, of course. It goes without saying."
At this, the TV studio audience applauded loudly.
"I went here and there among them, to chat," she continued.
Imitating a Jewish accent, Mrs Zakharova said Jewish people had told her: "'Marochka, understand this - we'll donate to Clinton, of course. But we'll give the Republicans twice that amount.' Enough said! That settled it for me - the picture was clear.
"If you want to know the future, don't read the mainstream newspapers - our people in Brighton [Beach] will tell you everything."
She was referring to a district of Brooklyn with a large diaspora of Jewish emigres from the former Soviet Union.
Russian opposition activist Roman Dobrokhotov wrote on Twitter (in Russian) that the spokeswoman had "explained Trump's victory as a Jewish conspiracy".
Michael McFaul, the former US ambassador to Moscow, commented on Facebook, "Wow. And this is the woman who criticizes me for not being diplomatic."
During the election campaign, Mrs Clinton accused Mr Trump of posting a "blatantly anti-Semitic" tweet after he used an image resembling the Star of David and stacks of money.
Mr Trump, whose son-in-law Jared Kushner is Jewish, dismissed the accusation as "ridiculous".
An exit poll by US non-profit J Street suggests an overwhelming majority of US Jews voted for Hillary Clinton in the presidential election.
A spokeswoman for Russia's foreign ministry has said Jewish people in New York told her they had mainly backed Donald Trump in the US election.