Despite flourishing research on the relationship between emotion and literal language, and despite the pervasiveness of figurative expressions in communication, the role of figurative language in conveying affect has been under-investigated. This study provides affective and psycholinguistic norms for 619 German idiomatic expressions and explores the relationships between affective and psycholinguistic idiom properties. German native speakers rated each idiom for emotional valence, arousal, familiarity, semantic transparency, figurativeness, and concreteness. They also described the figurative meaning of each idiom, and rated how confident they were on the attributed meaning. Results showed that idioms rated high in valence were also rated high in arousal. Negative idioms were rated as more arousing than positive ones, in line with results on single words. Furthermore, arousal correlated positively with figurativeness (supporting the idea that figurative expressions are more emotionally engaging than literal expressions) and with concreteness and semantic transparency. This suggests that idioms may convey a more direct reference to sensory representations, mediated by the meaning of their constituting words. Arousal correlated positively with familiarity. In addition, positive idioms were rated as more familiar than negative idioms. Finally, idioms without a literal counterpart were rated as more emotionally valenced and arousing than idioms with a literal counterpart. Although the meaning of ambiguous idioms was less correctly defined than that of unambiguous idioms, ambiguous idioms were rated as more concrete than unambiguous ones. We also discuss the relationships between the various psycholinguistic variables characterising idioms, with reference to the literature on idiom structure and processing.