Climate protesters Just Stop Oil set off an orange flare next to the 17th green at the 151st Open Championship at Royal Liverpool in Hoylake on Friday before being driven off the course by the police in a golf cart.
Orange powder was seen near the edge of the green just short of the putting surface but second-round play continued without delay.
A statement from tournament organisers the R&A read: "A protester was quickly apprehended on the 17th hole and is one of four people who have been arrested by the police. Play was not disrupted and we would like to thank the marshals, players and other spectators for their vigilance and understanding as the protesters were removed."
The Open becomes the latest sporting event in the UK to be targeted by the group of climate activists this summer. Just Stop Oil protesters also disrupted this month's Wimbledon Championships and the third Ashes cricket Test at Lord's.
The World Snooker Championship and rugby's Gallagher Premiership final were targeted earlier this summer.
Merseyside Police confirmed the four arrests on suspicion of conspiracy to commit criminal damage and public nuisance.
"Merseyside Police respects the right to protest and expression of views but antisocial, criminal behaviour or disorder will not be tolerated and will be dealt with robustly," the police force said in a statement.
"Police and R&A management will be looking to ensure the activities of anyone who wants to protest don't disrupt the event itself and if necessary we will used relevant legislation to deal those people involved in it."
"Contingency plans are in place to visitors enjoy these events in safety and with minimal disruption."