There is currently no data available on the vitamin B₁₂ content of biofertilizers containing purple photosynthetic bacteria or whether these biofertilizers contain “true B₁₂” or inactive corrinoid compounds (or both). Therefore, we tested the vitamin B₁₂ content of three commercially available biofertilizers containing purple photosynthetic bacteria. No or traces of vitamin B₁₂ were found in two of the biofertilizers (A and B) tested, while the third (C) contained a considerable amount (53.5 µg/L). To evaluate whether biofertilizer C actually contained vitamin B₁₂ or other corrinoids inactive in humans, the extracted compounds were purified using an immunoaffinity column and then identified as vitamin B₁₂ (main) and/or inactive corrinoids (minor, Factor III) using liquid chromatography electrospray ionization mass spectrometry (LC/ESI-MS/MS).