We report the successful moss-produced recombinant spider silk key protein component containing both the N- and the C-terminal domain. Spider dragline silk stands out as a remarkable biomaterial, representing one of nature's toughest fibres. Its strength rivals that of many synthetic fibres used commercially, rendering it applicable across various industrial and medical domains. However, its widespread utilisation requires cost-effective mass production. Biotechnology presents a promising avenue for achieving this goal, particularly through the production of recombinant dragline silk proteins in transgenic plant systems. This study aimed to assess the feasibility of producing one key protein component of dragline silk, MaSp1, from the western black widow spider, Latrodectus hesperus, the protein LhMaSp1, in the moss Physcomitrella (Physcomitrium patens). Here, we present the successful recombinant production of spider silk protein containing both the N- and C-terminal domains of LhMaSp1 in moss cells. The production of recombinant LhMaSp1 protein in Physcomitrella was performed in shake flasks and in five-litre photobioreactors and the correct synthesis of LhMaSp1 was proven via mass spectrometry. We estimate that the yield of recombinant spider silk protein in Physcomitrella bioreactors is above 0.82 mg/g fresh weight.