We report psycholinguistic norms for 305 French idiomatic expressions (Study 1). For each of the idiomatic expressions, the following variables are reported: knowledge, predictability, literality, compositionality, subjective and objective frequency, familiarity, age of acquisition (AoA), and length. In addition, we have collected comprehension times for each idiom (Study 2). The psycholinguistic relevance of the collected norms is explained, and different analyses (descriptive statistics, correlation and multiple regression analyses) performed on the norms are reported and discussed. The entire set of norms and reading times are provided as supplemental material.