In this work, a real-time PCR method was developed for the detection of fish in all kind of products, independent of the degree of transformation to which they have been subjected (as frozen or processed products) and compared with a commercial kit. Due to the high sensitivity and specificity of the method developed, it was thought to be appropriate for the analysis of cross-contamination in production chains, which would make it ideal to ensure food quality and safety, and protect the rights of the consumers to know what they are eating. In addition, it constitutes the first fast real-time PCR developed up to date for the detection of fish in all kinds of food including those that have been subjected to treatments (e.g., high temperatures and pressure) during processing.