Berizzo replaces Jose Angel Ziganda and is joined on the coaching staff by Ernesto Marcucci, Pablo Fernandez, Carlos Kisluk, Roberto Bonano and Mariano Uglessich.
Ziganda's departure was announced earlier in the month, the coach lasting a single season after succeeding Ernesto Valverde at San Mames.
The appointment of Berizzo, who required prostate surgery last season, sees the 48-year-old return to management after he was sacked by Sevilla last December.
"For me it's an honour to be here, to defend those common values that we have," Berizzo told a news conference on Thursday. "I appreciate all the confidence you've given me here, I hope to make Athletic better and have a defined style.
"I want to belong and be part of the Athletic philosophy, there is also a technical part and a sentimental part for the amount of people who have advised me to come here."