Officials are now frequently posting attention-grabbing messages to alert citizens to serious crimes and also to track down suspects.
The information gathered helped them carry out at least 300 arrests on drug charges last year.
The Spanish-language account @policia has the second-biggest following for a police force in the world, after the FBI.
It does not just help gather clues to crimes - it also helps spread information. Drugs = poo, even a child can understand that, goes one tweet. Get hooked and you are on a downer for life. Try to deal and you'll regret it forever. So popular have the messages proved, that they can easily gather 5'000 retweets.
Officials cannot believe their own popularity. It has been incredible for us but credit goes to the people who generously give us their trust and support, said Carlos Fernandez Guerra, from the digital strategy team of the Spanish National Police.
With the use of the information gathered on Twitter, in the past year the Spanish police have been able to warn people against new viruses and online fraud, continue the hunt for some of the most-wanted fugitives and arrest people accused of spreading child pornography on the internet.
Input from Spanish users of Twitter is proving a vital part of the strategy.
In the battle against drug-trafficking, Spanish police have made what they call tweet raids - attempts to use Twitter to solicit potential leads from tweeters.
The Spanish police first launched an online campaign to spread the word on Twitter, and provide internet users with a specific email account that guarantees confidentiality to facilitate online collaboration.
The force plans tweet patrols According to official figures, tweet raids led to the arrest of 300 individuals in Spain last year. We received about 11'500 emails containing valuable information thanks to one of our tweet raids, said Mr Fernandez Guerra.