A Spanish interpreter translates oral conversations between two or more people, speaking Spanish and one other language. An interpreter is similar to a translator, but the two terms are not completely interchangeable. In general, a translator is one who works with the written word, and usually only translates languages in one direction - i.e. Spanish to English, but not English to Spanish. These languages are referred to as the "source language" and the "target language." An interpreter, however, translates language orally, on-the-spot, and in both directions as needed.

There are two types of interpretation, known as simultaneous and consecutive. Simultaneous interpreters speak at the same time as the original language speaker, usually speaking through a microphone from another room. This type of Spanish interpreter needs to be able to think quickly, and have a working knowledge of the topics being discussed, so that he or she is able to listen and translate simultaneously, making sure to convey the true meaning of the sentence, while not missing any information. A consecutive Spanish interpreter, however, begins interpreting after the original speaker has completed a thought, and paused, allowing the time to interpreter to speak. Most consecutive interpreters will take notes as the original speaker is talking, so as to make sure the entire thought is conveyed accurately.

Because a Spanish interpreter needs to work much more quickly than a translator, he or she needs to have excellent grammar and language skills in both languages, along with an outstanding memory. Most people will find that they are better suited to either translating or interpreting, but typically not both. Some interpreters need to also study extra information on the subjects for which they will be interpreting; for example, court interpreters or medical interpreters are both highly specialized fields with specific terminology.

An interpreter must be aware of any cultural differences between the two languages to avoid inadvertently offending someone. Many interpreters are freelancers, though others might find steady employment working in a medical setting, such as a hospital, or in a judicial court, or government office. Many simultaneous interpreters are permanently employed by the United Nations. Though a degree is not required, many employers do wish their interpreters to have a degree, or at the very least complete a training program. To become a successful Spanish interpreter, it is necessary to be fluent in Spanish and at least one other language.