Turkey has long had a reputation for heavy smoking
Smoking has been banned from most enclosed public spaces in Turkey but smokers can still light up in cafes, bars and restaurants for another year.
The law, which builds on a ban affecting some public transport, also prohibits smoking in outdoor venues such as playgrounds and stadiums.
It aims to both discourage smoking and reduce secondary smoke health risks.
About 40% of adults - 25 million people - are smokers, making Turkey one of the world's hardest-smoking countries.
The new ban, which started at midnight (2100 GMT) on Sunday, applies to government offices, workplaces, shopping malls, schools and hospitals.
All forms of public transport, including trains, taxis and ferries, will also be affected but there will be exemptions for special zones in psychiatric hospitals and prisons.
Cafes, bars and restaurants will enjoy a transition period until they too come under the ban in July 2009.
'Law can help'
Anyone caught lighting up in a designated smoke-free area faces a fine of 50 Turkish liras (26 euros; $40).
One taxi driver said he did not think a ban would help him stop smoking cigarettes.
"I don't know how much of a deterrent these laws will be," he told The Associated Press.
"I cannot quit smoking, I'll only quit when I go to my grave. I have to smoke."
Baris Cirpici, a Turkish student, saw the law as a step in the right direction, despite reservations.
"The rules are too strict, but they are necessary," he told the Turkish Daily News.
"I am a smoker but I think this law can help many people quit smoking."