The American gave his home crowd in California plenty to cheer about after the judges scored the fight 117-111, 116-112 and 116-112 in his favour.
Aydin landed the heavier blows during the course of the bout, but 29-year-old Guerrero punched - and found his target - with greater frequency.
Guerrero had moved up two weight classes to meet Aydin in the hope victory would lead to a high-profile fight with the likes of Floyd Mayweather Jr. or Manny Pacquiao.
''I felt great at welterweight,'' Guerrero said. ''I wanted to fight the best and that's why I fought Selcuk. No one in the division wanted to fight him. He's been avoided.
"I came in and took care of business. I believe in my talents and I boxed and used my skills tonight.
''It felt great having all the support of my local fans and family here tonight. I'm back."
Turk Aydin claimed he lacked energy during the fight and asked his corner for sugar water in between rounds.
''The judges were not my problem. I was the problem,'' Aydin said. ''I couldn't do what I wanted to do. After the fourth round, something happened. It was like I was seeing double. But there's no excuse. I lost the fight.''