Led by Archbishop of Tuam Michael Neary, the ascent up the 2,510ft (765m) mountain, known as “the Reek”, began in the village of Murrisk at 7am.
Mayo Mountain Rescue said weather conditions were good for the climb with only a small number of minor injuries reported.
In a Mass service at the summit, the archbishop told pilgrims that, despite wealth and prosperity, people have not found inner joy.
“Today consumer values are often not creatively interpreted,” he said in the first service to be televised from the top of the mountain.
“True, they can seduce and reduce everything to wealth and security. The truly reflective person learns from this and probes deeper. In the midst of our recent wealth and prosperity we failed to find the inner joy, peace and faith that we might have expected.
“Faith enables and encourages us to search for meaning in the particular call we have received from God.”
The pilgrimage — which has been carried out uninterrupted for more than 1,500 years — is traditionally held on the last Sunday in July. About 100,000 people climb Croagh Patrick throughout each year.
Hundreds of first aid, civil defence and mountain rescue personnel were on duty during the day to assist the pilgrims, many of whom have climbed barefoot up the Reek, as it is known locally.
The mountain has been traditionally associated with St Patrick who, in 441, is said to have spent 40 days and nights fasting on the summit.
As the Catholic Church strives to attract more young men to the priesthood, the theme of this year’s climb was vocation.
The archbishop said vocation is a call to witness, service and love, and he urged people to ask themselves if God could be calling them to life as a priest or as a religious sister or brother.
“Today the priest is expected to be a man of courage, energy and compassion who wades into the impossible and makes things new.
“His ministry is a lifelong struggle to open up the world to God’s power and thereby transform human relationships.
“A new generation of priests will spring up when they see the full living of the Christian life in their homes, their schools, in their workplaces and parish communities.”