MOSCOW — A court in Moscow on Thursday released from pretrial detention one of the most prominent American businessmen working in Russia, whose arrest earlier this year had spooked foreign investors.

The arrest was all the more alarming as Michael Calvey, the founder and chief executive of the private equity company Baring Vostok, had been a consistent advocate for investment in Russia — even as many firms have retreated from the country, driven away by its struggling economy and worsening relationship with the West.

Mr. Calvey’s advocacy for investment continued despite two decades of government takeovers of companies, ruble devaluations and politically hued arrests, including that of Sergei L. Magnitsky, who died in pretrial detention and had been working as a lawyer for another prominent investor.

Yet Mr. Calvey, even in detention, continued to speak out in favor of the investment case for Russia, reading a statement to that effect on Thursday from inside the aquarium-like glass box where defendants are placed in Russian courts. In his remarks, he said the case against him was prompted by a business dispute.