WASHINGTON — A former lawyer for a powerful international corporate law firm was sentenced on Tuesday to 30 days in prison for lying to investigators in the special counsel inquiry about his communications with a Trump campaign aide and a Ukrainian businessman believed to be a Russian intelligence operative.

The former lawyer, Alex van der Zwaan, who is also the son-in-law of a Russian billionaire, was the first person to be sentenced in the investigation into Russia’s interference in the 2016 presidential election. He was also fined $20,000.

Mr. van der Zwaan admitted that he deceived investigators who interviewed him in November as part of their examination of contacts between the Ukrainian and two former high-ranking Trump campaign officials: Paul Manafort, once Mr. Trump’s campaign chairman, and Rick Gates, Mr. Trump’s deputy campaign manager. People familiar with the matter identified the Ukrainian as Konstantin V. Kilimnik, long Mr. Manafort’s right-hand man in Kiev, where he worked for years before joining the Trump campaign.

In an hourlong hearing, Mr. van der Zwaan’s defense lawyer argued that a fine was sufficient punishment because his client revealed what he knew in a subsequent interview.