New public health figures reveal 11,864 cases were reported across the state last year - of which more than a third were adolescent girls or young women under 24.
The actual number of cases is likely to be even higher as most infected people have no symptoms.
Pronounced as "kla-MID-ee-uh" Chlamydia, is a sexually transmitted disease (STD), which is caused by the bacteria Chlamydia trachomatis and can be cured.
Chlamydia is a very common cause of genital infection. The symptoms vary from an abnormal discharge (mucus or pus) from the vagina or penis or experience of pain while urinating. These early symptoms may be very mild. In most woman it goes unnoticed.
Experts fear teens who are too embarrassed to seek help or don't realise they are infected are creating a time bomb of irreversible fertility problems for their future.
It was most common in the teenage to 24 age group, with 4563 female cases and 2077 male cases.
Rates of other sexually transmitted infections, such as gonorrhoea and syphilis, have also surged in 2006, according to the NSW Health Public Health Bulletin.
NSW Health director of communicable diseases Dr Jeremy McAnulty said young people should heed safe sex messages, get tested if they had been in a risky situation and inform sexual partners if they discover they are infected.
"There is a real epidemic of chlamydia in young people,'' he said.
"The public health message is that it's a real health risk if you having unprotected sex.
"Diseases like chlamydia are easily treated but that's only if it's detected. For example, if you are a younger woman you might not have any symptoms until later on in life when you want to start a family and you have fertility problems.''
The repercussions of failing to get chlamydia diagnosed until later in life can be "expensive, painful and frustrating'' complications like pelvic inflammatory disease, ectopic pregnancies and infertility, he warned.