People from all around the country and of all ages are taking part, slowly ascending the rocky 765-metre holy mountain located a few kilometers outside Westport.
At least eight mountain rescue teams led by Mayo Mountain Rescue have been on Croagh Patrick since last night to aid any climber that sustains injury.
There were a number of minor injuries among the climbers, who were treated by paramedics.
An air ambulance helicopter that was located at the base of the mountain throughout the day was not required for any medivacs.
Traffic management and a parking plan were in place in Murrisk at the foot of the mountain, with plenty of parking available as some local people had opened access to roadside fields.