Stages, a cabaret tent and market zones will be set up in Cassiobury Park tomorrow as part of Herts Pride.
More than 20 acts are due to appear on various stages throughout the day, which organisers say all the family will be able to enjoy.
Herts Pride, now in its second year, will be opened by Elly Barnes, CEO and Founder of Educate and Celebrate, under the theme We Are Family.
The event starts at 11am and will run untill 9pm.
Elly said: "I’m very excited to officially open Herts Pride, it’s a complete pleasure and a great honour.
"I wholeheartedly believe that Pride events are incredibly important in keeping our journey to equality in people’s conscientiousness, to change hearts and minds and challenge the ongoing discrimination many LGBT people face. "Pride is an opportunity to celebrate but also a fantastic opportunity to educate about how we can create a prejudice-free society."
Thousands attended the first Herts Pride in Watford in 2013 and the organisers are expecting a big turnout again this year.
Herts Pride organiser Tyson Martin said this year's theme is a celebration of diverse families, same sex marriage, civil partnerships, relationships and friendships.
He said: "The Hertfordshire Pride Society is a group of friendly, passionate, creative volunteers from the local lesbian, gay men, bisexual and trans community and their straight allies who organise an annual Pride event in Hertfordshire Herts Pride."
Mr Martin continued Herts Pride is a family fun day event in Hertfordshire that aims to promote equality and diversity for the public benefit, through raising awareness of discrimination on age, disability, race, religion and belief, and in particular the elimination of discrimination on the grounds of sexual orientation and gender identity.
He added: "Herts Pride is proud to have Elly Barnes opening our event we believe that it is important that our Lesbian, Gay, Bisexual and Trans and straight ally youth feel empowered to find their places in the world, in their families, and in their communities."
People attending the event can find the Educate and Celebrate stall in the market zone and come and speak to representatives about how they can make their schools, colleges and workplace LGBT-friendly.
Herts Pride main event is free although there are three types of wristbands available if you want to access the Cabaret Marquee and licensed bar areas.
The cabaret marquee is £5 if purchased online in advance, or £10 on the day.
Whereas the wristband for Load of Hay in the Park Access All Areas is £20 online and not on sale on the day.
The VIP Wristband £10 in advance online, or £15 on the day.