The annual protestival at Preston Park, organised by Brighton Cannabis Club, seeks to change the law regarding the drug.
A spokesman for Sussex Police said: "Police attended the Green Pride protestival in Brighton on Saturday (July 20 ), which concluded with minimal disruption.
"The force had a noticeable presence at the event, held at Preston Park, due to the large number of people anticipated to attend.
"Working in conjunction with Brighton and Hove City Council, officers engaged with participants early on to ensure the boundaries were clear and that people were aware of the legislation around cannabis."
Police said one man was arrested on suspicion of possession with intent to supply cannabis and one man was arrested on suspicion of possession of cannabis.
Officers also made around 30 interventions where cannabis was seized from people and dealt with by various ways including community resolutions, a spokesman said.
Chief Inspector Chris Veale said: "We were able to actively engage with a number of groups, clubs and individuals associated with Green Pride, many of whom had travelled from across the UK.
“This enabled us to set the tone early and give people the opportunity to make the right decision based on the information provided.
"We made it clear that we would facilitate lawful protest, however we were also there to safeguard the public, particularly young people and children and to enforce the law, and most people responded positively to our engagement.
“There was a calm community feel throughout the day, and the vast majority of those in attendance were well mannered and good spirited.
"The peaceful crowd was reflected by the low level of law enforcement.”
Officers engaged with young people at the event, a spokesman said, and five teenagers were referred to the youth outreach service and their parents were contacted.
Anyone with any concerns in relation to drug use should report online to Sussex Police or ring 101.