Many Hong Kong residents believe the promotional gig by pro-democracy activist Denise Ho was cancelled after China's state-run media criticised the French company for allowing her to perform.
Ho was a leading activist during mass rallies in 2014 calling on Beijing to allow fully free elections.
The row comes as fears grow in the semi-autonomous city that Beijing is tightening its grip.
Dozens of protesters gathered at the central Times Square shopping mall this afternoon shouting: "Boycott Lancome!" and "Shame on self-censorship!"
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In the same building, a Lancome beauty centre and the offices of parent company L'Oreal were also closed.
Local media reported the company had issued an internal memo yesterday asking staff to take the day off.
Organisers warned of more action if the company does not respond to swelling public anger.
"The key point of this protest is to show the world that we should unite together and, through boycotting (their products), show Lancome and L'Oreal that you cannot just focus on the China market," said Avery Ng, chairman of the League of Social Democrats, one of a dozen groups planning to join the protest.
A petition on the website change.Org asking people to boycott Lancome products has gathered more than 4,000 signatures.
"The civilised world needs to stop kowtowing to China. Make an example of Lancome for disrespecting the people of Hong Kong and freedom," Lawrence Lau from Hong Kong, commented on the petition site.
Politicians have also voiced anger.
District councillor Christine Fong flushed her Lancome products down the toilet in a video posted on Facebook, watched more than 128,000 times.
The concert was also slammed on mainland social media with critics saying Lancome was using money from Chinese customers to support independence for Hong Kong and Tibet.
Hong Kong was returned to China in 1997 under a "One country, two systems" agreement and enjoys greater liberties than in mainland China, but there are fears these are being eroded.