Alexander Smirnov pleaded guilty in December to causing the creation of a false record after falsely telling his FBI handler that he had knowledge of bribes paid by executives at Burisma Holdings to Joe and Hunter Biden, according to court documents.
Hunter Biden served on the board of Burisma, a role that has attracted years of scrutiny from Republican lawmakers.
Smirnov also admitted to tax evasion.
Prosecutors working with Special Counsel David Weiss, who investigated matters related to Hunter Biden, had asked US District Judge Otis Wright in Los Angeles to sentence Smirnov to six years in federal prison.
"The defendant decided in 2020 to exploit the position of trust he enjoyed with the FBI in order to provide false information about one of the candidates for President of the United States in an attempt to influence the outcome of the election," prosecutors wrote in a court filing, referring to Joe Biden's 2020 campaign.
Lawyers for Smirnov sought a four-year prison sentence, arguing Smirnov had accepted responsibility and suffered a "personal downfall" resulting from the case.
Smirnov falsely claimed in conversations with the FBI that executives at Burisma told him in 2015 or 2016, while Joe Biden was vice president, that they hired Hunter Biden to "protect us, through his dad, from all kinds of problems".
Smirnov also fabricated a claim that Joe and Hunter Biden were each paid $US5 million ($A8.1 million) in bribes from Burisma executives, according to court documents.
Republican lawmakers learned of an FBI record documenting Smirnov's claims, which briefly became a focus of a since abandoned effort to impeach Joe Biden.
Weiss, the special counsel, also brought two criminal cases against Hunter Biden on tax and gun charges. Joe Biden issued a sweeping pardon for his son last month, ending both prosecutions.
