When learning spoken second language (L2), words overlapping in form and meaning with one's native language (L1) help break into the new language. When nonsigning speakers learn a sign language as L2, such overlaps are absent because of the modality differences (L1: speech, L2: sign). In such cases, nonsigning speakers might use iconic form-meaning mappings in signs or their own gestural experience as gateways into the to-be-acquired sign language. In this study, we investigated how both these phenomena may contribute jointly to the acquisition of sign language vocabulary by hearing nonsigners. Participants were presented with three types of signs in the Sign Language of the Netherlands (NGT): arbitrary signs, iconic signs with high or low gesture overlap. Signs that were both iconic and highly overlapping with gestures boosted learning most at first exposure, and this effect remained the day after. Findings highlight the influence of modality-specific attributes supporting the acquisition of a signed lexicon.