The law was championed by state Senator Alex Padilla.
Brochures must have the counts by July 2009. Menus and boards must list the information by 2011. Violators face fines of up to $500.
"Health and fitness are important to me and since I've taken office, I have waged a war on obesity and have promoted a healthy lifestyle," said Governor Schwarzenegger.
Those often scary calorie counts are supposed to help diners think about their girth before ordering. The Centers for Disease Control reports about a quarter of Californians are obese, meaning they are at higher risk for diabetes, heart disease, stroke and some cancers.
"In terms of the obesity epidemic, calories are really the most important piece of consumer information to provide consumers," said Harold Goldstein, California Center for Public Health Advocacy.
When showed how many calories they just ate or ordered for lunch, some diners went into sticker shock. However, some others didn't care.
"I wouldn't eat it. At least I would think twice from ordering it," said Erika Montoya, a diner.
Another diner, Julia, said she would still order her choice even if it carried 930 calories. However, Julia said, "I just really don't need the governor telling me what I should eat."
The California restaurant industry initially opposed the bill, but had to give in. Managers couldn't keep up with each county passing individual ordinances.
"Compliance issues, liability issues. One state law that's uniform to us makes the most sense," said Jot Condie, California Restaurant Association.
New York City already posts calories on menus. Studies show diners are eating, on average, 50 fewer calories because of it.
To help you with your healthier lifestyle, the governor also signed a bill this past summer making California the first state in the country banning trans fats from all restaurants beginning in 2010.