The article is dedicated to the study of the functioning of language means, which in the primary or secondary function are able to express the modality of probability in modern Spanish and Italian languages. We consider the category of probability as a kind of modal category both in terms of logical (epistemic) modality, functional grammar, and from the standpoint of the theory of linguistic communication. Probability as a kind of modality is one of the most common types of modality with a large gradation of semantic meanings - from complete ignorance to complete confidence. The range of language tools that can express this kind of subjective modality in Spanish and Italian seems vast. It is a functional-semantic category that combines different levels of language: modal adverbs, modal verbs, fixed syntactic constructions, forms of such moods as indicativo, subjuntivo, condicional in Spanish and indicativo, congiuntivo, condizionale in Italian, two forms of the future tense in both languages that are able to develop this modal meaning. All of them can interact with each other, reinforcing the studied modal significance. And so it is possible to express various gradation of probability. Due to the functional-semantic approach to the study of this category on the material of different languages, functional-semantic fields with central and peripheral zones were created. The structuring of these fields became possible due to the separation of primary and secondary probability modalities in the studied units. It seems that everything has already been said about this category, but a new round of interest in logical modality, adapting the concept of possible worlds to the category of probability, again raised the question of its content and caused the need to defend the fact that linguistic modality, although based on logical modality, does not identify with it.