The arrest highlights continuing evidence that drug production and trafficking is on the rise in Peru.
Desiree Colley, who had been in Lima for one week, hid the cocaine beneath a false bottom in her suitcase, police said on Sunday.
She told authorities that she would have been paid $5000 for the drugs in Madrid.
Peruvian police are increasingly discovering young foreigners in need of quick cash acting as couriers for drug traffickers.
Despite official attempts - supported by the United States - to stamp out cocaine production, Peru remains the world's second largest producer. Only Colombia produces more.
Drug seizures show farmers have
defied eradication campaigns
The Peruvian government has usually struggled to persuade farmers to stop cultivating coca, the lucrative plant used to produce cocaine.
According to the United Nations Office on Drugs and Crime, more than 46,000 hectares in Peru in 2002 was used to grow coca. The UN figure has risen for the third consecutive year.
The White House Office of National Drug Control Policy estimates Peru produces about a fifth of the roughly 770 tonnes of cocaine exported annually in recent years to the US and Europe.