The Argentine, who has spent the last year in Brazil coaching Atletico Mineiro, was appointed by Marseille last Friday.
The ex-Chile, Argentina and Sevilla boss, who has signed a contract until 2023, is the permanent successor to Andre Villas-Boas in charge of the former Champions League winners.
Villas-Boas was suspended by the club a month ago following a disagreement over transfers. On Tuesday Marseille confirmed that they had finally officially parted company with the Portuguese "by mutual agreement".
Since Villas-Boas was removed from the dugout, interim coach Nasser Larguet has overseen the team's last seven games, losing just once, to Paris Saint-Germain.
Larguet will still be in charge when OM, who are seventh in Ligue 1, go to table-toppers Lille on Wednesday as part of a full card of midweek fixtures.
French government regulations stipulate that anyone entering the country from outside Europe must self-isolate for seven days on arrival and present a negative Covid-19 test at the end of that period.
"I don't see how he can get out of it," one source inside the club told AFP.
It will mean the first game he can take charge of will be the league game against Rennes on March 10.
Sampaoli's appointment came the same day the club's owner, Frank McCourt, named 34-year-old Spaniard Pablo Longoria -- previously the sporting director -- as Marseille's president, replacing the unpopular Jacques-Henri Eyraud.
"It is a big responsibility that I have given him but I know it is a job he is capable of," American tycoon McCourt said of Longoria in an interview with local newspaper La Provence.
"There are people who have a unique talent, regardless of their age. Some people are born leaders," added McCourt, who is currently in Marseille for the first time since the end of 2019 in an attempt to ease the tension around the club.
Several hundred Marseille fans stormed the training ground in an angry protest at Eyraud's running of the club at the end of January.
McCourt called those involved in the attack "thugs" and compared the incidents to the deadly January 6 assault on the US Congress.
Last week one man was jailed for three months and 11 more got six-month suspended sentences for their involvement in the events.
Standout matches today