Second-placed Lyon opened the door for either Marseille or Monaco to overtake them when they were beaten by Bordeaux earlier in the day, but the two sides were forced to settle for a share of the spoils at the Stade Velodrome.
Just one point now separates second from fourth, although Monaco remain outside the Champions League spots with Marseille hanging on to their place in third.
The defending Ligue 1 champions were rampant on their way to a 6-1 win in the reverse fixture, and the home fans may have been fearing that a similar hiding was on the cards this evening when the visitors took the lead after only four minutes.
Balde Keita latched on to a pass on the edge of the box and his first touch left him with only the keeper to beat, which he did with aplomb by tucking the ball into the bottom corner.
However, Marseille responded to that early setback almost immediately when defender Adil Rami found himself in the opposition box and nodded home from close range after Florian Thauvin's deflected strike had looped into his path.
The hosts should have taken the lead shortly before the half-hour mark when a low cross from the right found its way through to Dimitri Payet, but the former West Ham United playmaker blasted a glorious chance over the crossbar with the goal gaping.
As it was, the two sides went into the break all square, but it took just two minutes for Marseille to take the lead after the restart, with Payet going some way towards atoning for his miss by providing the assist.
Just as Marseille were quick to respond to falling behind early in the first half, so were Monaco early in the second half and parity was restored just four minutes later when Fabinho - who recently suggested that his time at the club could be coming to an end - bundled his way past three defenders before placing his finish in off the inside of the post.
Monaco thought they had regained the lead again in a topsy-turvy contest just six minutes later when Jemerson powered a towering header into the corner, but this time their celebrations were cut short by the linesman's flag.
Marseille quickly hit back and almost got their noses in front again just two minutes later when Morgan Sanson's volley from the edge of the box flashed just past the post.
Sanson came close once more with just six minutes remaining - again with a volley from the edge of the box - but this time it flew narrowly over the crossbar as the two sides were forced to settle for a share of the spoils.
The result brings an end to Marseille's six-match winning streak across all competitions, although they have now lost just one of their last 18 league games and only one of their last 16 at home.
Monaco, meanwhile, are now unbeaten in their last eight Ligue 1 outings but remain a point off the Champions League places in a fascinating three-way battle for just two spots.
MARSEILLE (4-2-3-1): Mandanda; Sarr, Rami, Rolando, Sakai; Sanson, Dias, Thauvin, Payet (N'Jie, 84'), Ocampos (Zambo Anguissa, 49'); Germain (Mitroglou, 92')
MONACO (4-2-3-1): Subasic; Toure, Glik, Jemerson, Sidibe; Tielemans, Fabinho, Ghezzal (Lopes, 69'), Moutinho, Balde; Falcao