The son of former San Francisco 49ers head coach, Dick Nolan, he signed with the 49ers in 2005 to be head coach, following in his father's footsteps. Nolan joined San Francisco after establishing himself as the defensive coordinator of the Baltimore Ravens, a position he held with three other teams: New York Jets (2000), Washington Redskins (1997-99), and New York Giants (1993-96).
Nolan finished the 2005 season with a 4-12 record, but he managed to field a more competitive team than the previous year. The 49ers managed to be competitive at home, improving on the 2-14 record posted under Dennis Erickson in 2004.
Following his hiring by the 49ers, Nolan asked the NFL for permission to wear a suit and tie on the sidelines as a tribute to his father. The league denied Nolan's request because of the contract it has with apparel companies for its coaches to wear team-logo attire. Nolan would abide by the ruling.