A French exchange student organized the demonstration at Sergels Torg, using Facebook to spread the word.
"Yesterday, it felt horrible to be abroad," he told news agency TT, adding, "I just wanted to be with other French people, other Swedes, other people for strength. I am dumbfounded."
Among those present at the demonstration was France's ambassador to Sweden, Jacques Lapouge, who also met with Prime Minister Stefan Löfven of the Social Democrats today. Löfven went to the embassy to deposit flowers on Saturday, and to sign a condolence book. Other political leaders also lay flowers at the embassy, including Åsa Romson and Gustav Fridolin of the Green party.
Lapouge told Swedish Radio News, "It's very important in this difficult time to count on the solidarity of our friends in Europe and particularly in Sweden."
In another demonstration of support for France, the TV tower, Kaknästornet, in Stockholm, has been lit in the red, white and blue of the French flag.