Lord Bell said in an interview with independent Belarusian news agency Belapan that a contract was signed late last week, but did not disclose the size or term of the contract.
He has pledged to work on improving the image of the country, rather than that of President Alexander Lukashenko, dubbed "Europe's last dictator" by Washington, while conceding that a president is an undeniable part of a county and its image.
Lukashenko, president since 1994, and other top Belarusian officials are currently banned from visiting the European Union, including the U.K., for their clampdown on political dissent and other human rights violations. Lukashenko expelled the U.S. ambassador in March and recalled Belarus's ambassador from Washington.
The deal with Bell came after nearly five months of talks between the spin doctor and Belarusian authorities, Russian daily Kommersant said. Lord Bell met with Lukashenko in Minsk in March, and noted "a lot of double standards" in Western policies toward the country and biased media coverage.
Media reports said earlier the PR executive had planned two campaigns for Belarus, focused on information and marketing, to send a "more factual message about Belarus" and improve the country's investment image.
According to Kommersant, Bell earlier said he and his company expected to earn "millions of dollars" in ex-Soviet Belarus.
Lord Bell advised Lady Thatcher on interviews, clothing and even her hairstyle, consulted a Saudi government, Iranian leader Mahmoud Ahmadinejad, Thailand's controversial ex-premier Thaksin Shinawatra, and Russian fugitive oligarch Boris Berezovsky. However, Bell did turn down Zimbabwe's dictator, Robert Mugabe.
Bell has avoided commenting on a police crackdown on opposition activists in Minsk on March 25, when dozens of protesters and journalists were beaten up. The United States and the EU condemned the handling of the rally by authorities.