Introduction Reliable, well-maintained laboratory equipment is essential for timely, accurate and reliable laboratory results for patient care, surveillance, and health system resilience. Tanzania implemented the Standard Medical Laboratory Equipment Guideline (SMLEG-2018) to harmonise procurement and improve efficiency across a tiered laboratory system and network. However, equipment functionality gaps remain a critical challenge for healthcare delivery. This study determined the functionality status of standardised laboratory analysers in Tanzania mainland and identified the drivers of non-functionality. Methods We conducted a facility-based cross-sectional study to identify the causes of non-functionality of standardised chemistry, haematology, and urine analysers across mainland Tanzania. We assessed 3,044 analysers and used Pareto analysis to identify the primary drivers of non-functionality. Results Of the 3,044 standardised analysers assessed, 987 (32.4%) chemistry 1,308 (43.0%) haematology, and 749 (24.6%) urine) assessed; 397 (13.0%) were non-functional. Proportionally, urine analysers were the most non-functional (n=176/749, 23.5%), followed by chemistry (n=135/987, 13.7%), and haematology (n=86/1308, 6.6%) analysers, p