Prosecutors said the five men shot and killed 77-year-old Bishop Luigi Locati in July 2005 after a row over cash donated to the Isiolo diocese.
The popular Locati was slain at the church compound in Isiolo, some 250 kilometres (150 miles) north of the capital, in what prosecutors said was a power struggle for control of the diocese and its cash ahead of the bishop's retirement.
After an eight-year trial, Father Waqo Guyo was named as the mastermind of the plot, having recruited Mohammed Molu Bagajo, Aden Ibrahim Mohamed, Mahati
Ali Halake, and Roba Balla Bariche to carry out the killing.
"The priest planned, financed, facilitated the acquisition of the gun and recruited the co-accused persons to execute the plan to kill the bishop," Judge Fred Ochieng told the court in Nairobi.
The five, who all denied the murder, will be sentenced on Thursday.
Locati, from the northern Italian province of Vercelli, was ordained a priest in 1952 and came to Kenya 10 years later. He set up the Isiolo diocese in 1963.
The murder outraged many Kenyans with hundreds – including then President Mwai Kibaki – attending his funeral in Isiolo.
A sixth man, Diga Wario, was acquitted of the murder.