Institutions of higher learning in Kenya have traditionally used paper-based attendance registers, which have been seen to lack validity for decision-making. There is a trend to adopt Biometric attendance registers in a number of institutions, however, they still have usability issues. This study uses a modified Technology Acceptance Model (TAM) to investigate the usability of the fingerprint biometric students' attendance register system. The original TAM used perceived usefulness, and perceived ease of use, as the test factors for acceptance of technology. Researchers have modified the TAM to include more test factors such as attitude toward use, and trust and security. In this study, we use the extended TAM-TRA model. The model includes the attitude toward, trust, and security in using the technology, in addition to the original perceived usefulness, and perceived ease of use, to conduct usability of the fingerprint attendance register system. These are important factors in the successful implementation, acceptance, and adoption of such systems. The study applies quantitative and qualitative surveys and observations, to collect data from sampled users of the fingerprint biometric attendance register system and test its usability using the modified TAM. A class of twenty students at the Technical University of Mombasa interacted with the fingerprint biometric attendance register system, and for each student, the usability tests were carried out, recorded, and analyzed. The perceived usefulness, perceived ease of use, attitude toward use, trust, and behavioral intention to use, scored 88.75%, 70%, 77.5%, 65%, and 77.5% levels of acceptance respectively. The contribution of this paper is in the insight to organizations that seek to improve the acceptance of their biometric recognition systems.