The Corsican side took the lead when Guinean Sadio Diallo beat goalkeeper Danijel Subasic from close range.
But Portugal midfielder Bernardo Silva pulled the league leaders level early in the second half when he headed in an Almamy Toure cross.
Champions Paris St-Germain would move to within a point of the summit should they beat Toulouse on Sunday.
Monaco travel to face Manchester City in their Champions League last-16 first-leg game on Tuesday.
Match ends, Bastia 1, Monaco 1.
Second Half ends, Bastia 1, Monaco 1.
Delay over. They are ready to continue.
Delay in match Jean-Louis Leca (Bastia) because of an injury.
Foul by Benjamin Mendy (Monaco).
Jean-Louis Leca (Bastia) wins a free kick in the defensive half.
Fabinho (Monaco) wins a free kick in the defensive half.
Foul by Lenny Nangis (Bastia).
Attempt missed. Thomas Lemar (Monaco) left footed shot from very close range is high and wide to the right. Assisted by Bernardo Silva with a cross.
Lenny Nangis (Bastia) is shown the yellow card.
Attempt missed. Florian Marange (Bastia) header from the centre of the box is too high. Assisted by Axel Ngando with a cross following a corner.
Corner,  Bastia. Conceded by Benjamin Mendy.
Attempt missed. Jemerson (Monaco) header from the centre of the box misses to the right. Assisted by Thomas Lemar with a cross following a corner.
Corner,  Monaco. Conceded by Jean-Louis Leca.
Attempt saved. Kylian Mbappe (Monaco) right footed shot from the right side of the box is saved in the bottom left corner. Assisted by Bernardo Silva.
Foul by Bernardo Silva (Monaco).
Lassana Coulibaly (Bastia) wins a free kick in the defensive half.
Attempt missed. Kylian Mbappe (Monaco) left footed shot from the centre of the box is high and wide to the left. Assisted by Benjamin Mendy.
Bernardo Silva (Monaco) wins a free kick in the defensive half.
Foul by Lenny Nangis (Bastia).
Substitution, Bastia. Lenny Nangis replaces Gaël Danic.
Attempt missed. Falcao (Monaco) right footed shot from the centre of the box is too high. Assisted by Nabil Dirar with a cross.
Substitution, Monaco. Nabil Dirar replaces Almamy Touré.
Attempt missed. Jemerson (Monaco) header from the centre of the box is high and wide to the left. Assisted by Thomas Lemar with a cross following a corner.
Corner,  Monaco. Conceded by Florian Marange.
Corner,  Monaco. Conceded by Alexander Djiku.
Attempt missed. João Moutinho (Monaco) right footed shot from outside the box is too high following a corner.
Corner,  Monaco. Conceded by Abdelhamid El Kaoutari.
Foul by Thomas Lemar (Monaco).
Prince Oniangué (Bastia) wins a free kick in the defensive half.
Almamy Touré (Monaco) wins a free kick in the defensive half.
Foul by Gaël Danic (Bastia).
Substitution, Bastia. Axel Ngando replaces Sadio Diallo.
Substitution, Monaco. Kylian Mbappe replaces Valère Germain.
Foul by Fabinho (Monaco).
Sadio Diallo (Bastia) wins a free kick in the defensive half.
Attempt missed. Valère Germain (Monaco) header from the left side of the box is too high. Assisted by Benjamin Mendy with a cross.
Corner,  Monaco. Conceded by Alexander Djiku.
Attempt blocked. Bernardo Silva (Monaco) left footed shot from outside the box is blocked.
Bernardo Silva (Monaco) wins a free kick on the right wing.
Monaco missed the chance to go six points clear at the top of Ligue 1 after being held by Bastia.