Mihajlovic initially rallied against criticism aimed in his direction after Serbia finished third in Group A behind Belgium and Croatia, insisting he wanted to lead the country through Euro 2016 qualifiers, but opted instead on a return to Italy.
"I have decided to leave the Serbian national team and take up Sampdoria's offer... but I am sad because of it," Mihajlovic told reporters after leading the national team in a traditional friendly against a select XI in the central city of Uzice on Tuesday.
"Money had nothing to do with it nor did Sampdoria's call trigger my departure. It happened because the Serbian Football Association (FSS) president Tomislav Karadzic and secretary general Zoran Lakovic couldn't vouch that they would carry on."
Karadzic and Lakovic had stood firmly behind Mihajlovic despite poor results and also backed his strict code of conduct, which saw gifted forward Adem Ljajic expelled from the national set-up because he refused to sing the anthem in a friendly.
There was no immediate confirmation over Mihajlovic's appointment from Sampdoria, who are 18th in Serie A following just two wins from their opening 12 games.
The former defender spent a number of years in Italy playing for Roma, Lazio, Inter Milan and Sampdoria, where he scored 12 goals in 110 league appearances from 1994-98.
They fired coach Delio Rossi last week following a 2-1 defeat at Fiorentina and host Lazio in their next league match on Sunday.
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