Organizer Hadi Damien said a concert planned for Saturday at The Palace theatre was axed after the venue received threatening phone calls and posts on social media, as well as pressure from religious institutions.
The cancellation comes after death threats prompted a Lebanese festival in July to pull an appearance by one of the Middle East's most popular bands, Mashrou' Leila, which has a gay frontman, leading to fears of a crackdown on LGBT+ rights.
"Religious authorities and figures started to speak up and ask the authorities ... to make sure Pride doesn't happen any more," Damien told the Thomson Reuters Foundation by phone.
"It went quite crazy ... People were threatening the owner of the venue."
Lebanon, which became the first Arab country to hold a gay pride week in 2017, has been seen as a beacon of freedom in the conservative region and more socially liberal.
It is, however, illegal to have gay sex in Lebanon where laws prohibit "unnatural" sex, without giving further definition.
Last year a Lebanese judge said that same-sex relations do not contradict laws of nature, a move welcomed by rights activists. But lesbian, gay, bisexual and transgender people say they still face discrimination by state and society.
Lebanon's ministry of justice and interior ministry could not be immediately reached for comment.
The country's second pride week, which involved about 2,700 people attending about six events, was stopped after three days in 2018 when police raided an event and arrested Damien.
Damien said although the opening night of Beirut Pride had been cancelled, the remainder of the events scheduled to run from Saturday until Oct. 6 would go ahead as planned in various cultural centres, bars and restaurants.
He said a permit to stage the country's first pride march had been submitted and he was hopeful, despite the setbacks.
"There is nothing in the world that goes backwards," Damien said.