The study examined the effect of academic librarians’ years of experience on their awareness and utilization of the Z39.50 protocol for cataloguing in federal and state university libraries in South-South Nigeria. This study utilized descriptive survey research design. The population of this study was 262 academic librarians, made up of 97 academic librarians from federal universities and 159 academic librarians from the state university libraries. The study used census sampling technique to sample all the 262 academic librarians that constitute the population of the study. A self-structured was used for data collection. Data obtained from the study was analysed using descriptive statistics of mean score and standard deviation, while the corresponding null hypotheses were tested using independent sample t-test.  The findings revealed that librarians with 16 years and above of work experience demonstrated a higher level of awareness of the Z39.50 protocol compared to their less experienced counterparts. However, in contrast, librarians with 0-5 years of experience exhibited the highest extent of utilization of the protocol, indicating that awareness does not necessarily translate into practical application. Furthermore, the study established a significant difference in both awareness and utilization of the Z39.50 protocol based on years of work experience. The study concludes that while more experienced librarians are aware of the protocol, they may not actively engage with it as much as their less experienced colleagues, who are likely more familiar with digital cataloguing tools and automated systems. It was therefore, recommended that targeted training and capacity-building initiatives that encourage greater adoption of the Z39.50 protocol among all academic librarians, ensuring that both awareness and utilization levels are aligned for improved cataloguing efficiency in university libraries.