This paper investigates the morpho-phonological differences between the members of related noun-verb pairs in Catalan Sign Language. Like parallel investigations in other sign languages, our experimental work provides evidence that the major differentiating factors between related nouns and verbs materialize in the movement component of signs and non-manual markers, thus providing empirical support to the hypothesis that most noun-verb pairs have different morpho-phonological properties. We distinguish different types of movements, which we categorize into four regular morphological subgroups. We also take into account a fifth group that shows no apparent movement distinction. Concerning non-manual markers, we provide empirical evidence that nouns are mostly produced simultaneously with mouthing, in contrast to verbs, which in a smaller proportion are produced mainly with mouth gestures. Crucially, the fifth group presents the largest ratio of mouthing for nouns and even for verbs. We address these findings within an exo-skeletal theoretical syntactic approach (Borer 2005a,b, 2013, 2014).