Willis, whose deal has a maximum value of $16.7 million with $12 million in guaranteed money, is one of several key players the 49ers added during a busy offseason.
"I'm a team player and I wanted nothing more than to be on time and be here for camp," said Willis, the 11th overall pick out of Mississippi. "(The deal) was done on time, I'm here for the start and it's a blessing to me. My job now is to come in here and give the 49ers and the organization and my teammates everything I've got, and I'm willing to do that."
San Francisco spent $40 million in guaranteed money to bring in five potential starters in free agency, then added receiver Darrell Jackson via trade.