The government of President Maithripala Sirisena unseated Rajapaksa in 2015 on promises to expose corruption and is under pressure to follow through.
Sirisena's administration has been probing money laundering and misappropriation of state property in more than 50 cases, but no one had been convicted until Thursday.
Colombo High Court sentenced Lalith Weeratunga, former secretary to Rajapaksa, and Anusha Palpita, ex-head of the state-run Telecommunication Regulatory Commission, to three years of "rigorous imprisonment", or jail with hard labour, and fined them 52 million rupees ($340,760) each.
Election monitors had complained that the state fund was used to influence voters ahead of 2015 presidential polls. Kalinga Indratissa, the lawyer who appeared on behalf of Weeratunga and Palpita, told Reuters the two would appeal.
Two of Rajapaksa's sons, Namal and Yoshitha, have been arrested and released on bail over money laundering allegations.
Rajapaksa and his family deny any wrongdoing.
Rajapaksa was president for a decade until January 2015 and is popular among ethnic majority Sinhala Buddhists who credit him with ending the 26-year-war against minority Tamil separatist rebels in 2009.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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