Carlo Ancelotti has turned down the chance to return to AC Milan, telling the club he needs rest.
Jose Mourinho insists Diego Costa is content at Chelsea in response to reports linking him with a return to Atletico Madrid.
The Genoa outfit offered the 44-year-old the job after dismissing Delio Rossi during the international break.
"After talks with the (Serbian) federation I have decided that I will no longer be the coach of Serbia," Mihajlovic said on the Serbian Federation's website, www.fss.rs.
"My contract was due to expire at the end of the month.
"I have taken this decision with much regret, because I set up a new generation and a new team for Serbia who have bright future.
"I have accepted the offer from Sampdoria, where I played for four years.
"I would like to emphasise that Sampdoria's invitation had little influence on my decision, as I have left because federation president Tomislav Karadzic and secretary Zoran Lakovic could not guarantee they would remain in their roles.
"I leave the door open to maybe one day return and coach Serbia again."
The former Yugoslavia international took over the national team in May 2012 but was unable to lead Serbia to a place in next year's World Cup in Brazil.
Serbia finished third in Group A behind Belgium and Croatia.
Mihajlovic, who played 14 seasons in Italy's top flight, has coached Bologna, Catania and Fiorentina in Serie A.
He is expected to be unveiled at Sampdoria in the next 24 hours.
Samp are 18th in the standings, with two wins from 12 games.