Lisandro Lopez's late dismissal meant that the previously-threatening visitors had to abandon their quest for victory and hold out for a draw at the Stade Louis II.
The Portuguese outfit remain bottom of the table, while Monaco are second behind Bayer Leverkusen having yet to lose in Europe this campaign.
Below, Sports Mole analyses whether the result was reflective of the action.
On target: 2
On target: 4
Was the result fair?
A draw was probably the fairest result at the end of a contest between two teams who were distinctly lacking a cutting edge. Both had their periods on top, with Benfica in particular pressing for a winner in the second half. Lisandro Lopez's late sending-off gave Monaco the momentum, but they were not good enough to capitalise.
It is no surprise that Monaco have had trouble scoring this season. They have only one goal in three Champions League games, and are hardly firing on all cylinders domestically either. The first-half injury withdrawal of Dimitar Berbatov did not help, but they created so few genuine chances, and when they did, Lucas Ocampos sliced horribly over when faced with an open goal. They do not seem to have any clear type of attacking approach, and they no longer have the stars to bail them out with individual ability. From goalkeeper Danijel Subasic, who was excellent, through the centre-backs and midfield, they have a solid spine, but a lack of creativity is harming them in the final third.
Provided more of an attacking threat than the hosts over the course of the 90 minutes as Eduardo Salvio and Nicolas Gaitan especially caused problems when they ran with the ball at pace. Lima is not the focal point of the attack that Oscar Cardozo was, though, and they could do with a more physical presence as their lone frontman for their bunch of skilful midfielders to bounce off. The central defensive pair of Luisao and Lisandro Lopez were commanding in the air, but did not have the pace to keep up with Anthony Martial when the substitute striker ran in behind. Fortunately for them, Monaco were not capable of finding him on enough occasions to consistently trouble the visiting backline. Lopez's late dismissal was a foolish lack of discipline which cost his side the chance to push for victory in the final 15 minutes.
Sports Mole's man of the match
Danijel Subasic: The Croatian goalkeeper made a good reaction save to keep out Lima in the first half, and was then called upon several more times to keep Monaco level during Benfica's spell in the ascendancy midway through the second. A one-handed stop from Gaitan, the match's other outstanding player, was most impressive.
Ocampos will have nightmares tonight about his eighth-minute miss. Berbatov had broken the offside trap and unselfishly squared to the winger, who had the majority of the goal to aim at when he sliced over from eight yards following a horrible bobble. Things could have been so different had that gone in.
With the culprit having already been booked, Szymon Marciniak had little choice but to give Lopez his marching orders for a lunge on Joao Moutinho, but was right to decide that the offence was a straight red card, which is an important distinction when it comes to suspensions. Elsewhere he missed a couple of seemingly obvious bookings, but it was generally an easy night's work for the Polish referee and his officials.
Monaco: Leonardo Jardim's side face Bastia and Reims before the return fixture at the Estadio da Luz.
Benfica: They put their unbeaten domestic record on the line against a competent Braga side on Sunday.