The 44-year-old had been linked with his former club, for whom he made over 100 appearances as a player, for some time.
He has now confirmed he will return for a fourth managerial stint in Italy, while admitting regret at leaving the national post he accepted in May 2012.
"In recent days questions were raised over my future, because my contract was due to expire at the end of the month," Mihajlovic told reporters.
"Out of respect for Russia (who Serbia played in a friendly on Friday) and the journalists, I stayed quiet until the final two games were played, but after talks with the federation I decided that I will no longer be the coach of Serbia.
"I make this decision with much regret, because I set up a new generation and a new team for Serbia who have bright prospects.
"I accepted the invitation from Sampdoria, where I played for four years."
Mihajlovic has suggested he would have left Serbia regardless of the approach from Sampdoria, who sacked Delio Rossi last week.
"I want to emphasise that Sampdoria's call had little influence on my decision, as I left because federation president Tomislav Karadzic and secretary Zoran Lakovic could not guarantee they would stay in their roles," he added.
"I leave the door open to maybe one day come back and be coach of Serbia again."
Sampdoria currently lie 18th in Serie A, having won just two games this season.
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