Magnetosomes are natural magnetic nanoparticles with exceptional properties that are synthesized in magnetotactic bacteria by a highly regulated biomineralization process. Their usability in many applications could be further improved by encapsulation in biocompatible polymers. In this study, we explored the production of spider silk-inspired peptides on magnetosomes of the alphaproteobacterium Magnetospirillum gryphiswaldense. Genetic fusion of different silk sequence-like variants to abundant magnetosome membrane proteins enhanced magnetite biomineralization and caused the formation of a proteinaceous capsule, which increased the colloidal stability of isolated particles. Furthermore, we show that spider silk peptides fused to a magnetosome membrane protein can be used as seeds for silk fibril growth on the magnetosome surface. In summary, we demonstrate that the combination of two different biogenic materials generates a genetically encoded hybrid composite with engineerable new properties and enhanced potential for various applications.