Antigen identity, quantity and integrity are key factors to be evaluated as part of consistency testing of tetanus vaccines. Here we have developed a monoclonal antibody sandwich ELISA to measure the relative amount and quality of tetanus toxoid (TTxd) in human and animal tetanus vaccines. The ELISA is highly specific, has good dilutional linearity, and is suitable for detecting TTxd in a range of different products. We have demonstrated the ability of the assay to discriminate between batches of different content, using vaccine batches that had been prepared to contain differing amounts of TTxd, and of different quality, using samples of non-adjuvanted TTxd that had been exposed to sonication and final lot vaccines that had been exposed to heat or oxidative stress. We have also demonstrated successful transfer of the method to other laboratories and have shown that different tetanus antigen materials may be able to serve as a reference antigen for standardization of the method. The results show this test has the potential to play a key role in a control strategy no longer including an in vivo potency test.