Metal-organic frameworks (MOFs) are porous coordination polymers (CP) produced by metal-based nodes and multitopic organic ligands. Based on their porous and microcrystalline powder structures, they have initiallybeen used for storage, catalysis and separation. Then, because of their advantageous properties like ease of the tailoring, they also have been applied in areas like chemical sensing, biological applications, etc. The CPs were combined with molecules such as organic dyes, small biomolecules, nanomaterials like nanoparticles, nanowires, nanofibers and polymers and as a result, composite MOFs have been produced. By this way, better mechanical stability, conductivity, and catalytic performance were obtained. This review (with 135 refs.) summarizes the progress made in the past years in the field of electrochemical and optical sensing based on the use of MOFs. Following an introduction into the field, large sections cover MOF based sensors exploiting (a) carbon nanomaterials (with subsections on carbon nanotubes, graphene and its derivatives), (b) metal/metal oxide MOFs; including gold, silver, copper and/or copper oxide nanoparticle and other metal/MOF composites. Enzyme mimicking MOFs are discussednext. In this context, after the brief information about focused MOFs, the nanomaterial/MOF composites were discussed and related examples were presented.