Biomolecules performing specific biological functions on material surfaces are progressively employed in the development of miniaturized bioassays, biosensors, bioelectronic devices, and medical equipment. Device performance is improved with covalently immobilized bioconstituents. The unique advantages of using light-controlled reactions to achieve biomolecule immobilization on surfaces are addressed. On activation of introduced light-sensitive reagents, biomolecules are covalently linked to material surfaces. Procedures leading to light-dependent engineering of surfaces are exceptionally facile. Immobilization by light is compatible with biological functions, enabling surface patterning and molecular coating of materials. Current strategies and protocols are illustrated with selected examples of biomolecule photoimmobilization.