Gabrielle Hutchinson, 23, who was working as a security contractor that night died in hospital early yesterday.
The concert, by Afro-pop singer Asake, at the Brixton Academy, was cut short after people tried to force their way inside, the Met Police said.
It follows the death of Rebecca Ikumelo, 33, on Saturday, as third woman remains in a critical condition and is continuing to receive treatment in hospital following the crush at the sold-out show.
The Met said: "At this time we have established that the three women who were critically injured, including Rebecca Ikumelo and Gabrielle Hutchinson who have tragically died, were all in the foyer of the building." It added that detectives were working hard to establish exactly what happened and described the investigation as "large and complex".
Officers are reviewing CCTV, phone footage, speaking to witnesses and conducting forensic examinations. Florence Eshalomi, the MP for Vauxhall whose constituency includes Brixton, said that she felt heartbroken by the deaths of the two women.
Ch Supt Colin Wingrove, policing commander for Lambeth and Southwark, said: "It is devastating news that a second person has lost their life following the events on Thursday. I wish to express my heartfelt condolences to Gabrielle's family at this unimaginably difficult time."
