The study focused on the assessment of quality control tests in X-ray units from the Southern regions of Tanzania to yield the data required to create and implement quality control policies and strategies. Quality control tests were conducted on twenty-six diagnostic X-ray units in private and government hospitals in southern regions of Tanzania during 2020 – 2021. The tests focused on the reproducibility of accelerating tube potential, time reproducibility, the accuracy of accelerating tube potential, half-value layer, beam alignment, and collimation. The statistical analyses were done by using the Microsoft Excel spreadsheet of 2013. The results were compared with the tolerance limits.  Of all X-ray units evaluated, 92.31% had kVp accuracy within the tolerance limit of 5% and 92% of the X-ray units had acceptable HVL values ≥ 2.3 mm Al at 80 kVp. Moreover, results have shown that 86.96% and 82.61% of X-ray units had acceptable beam collimation (≤ ±2 cm) and beam alignment (≤3% of the X-ray source and X-ray table), respectively. Comprehensive regulatory inspections and equipment maintenance plans in the Southern zone is significantly required due to the high patient workload which attributes frequent breakdown of X-ray units. Moreover, radiographers need to be trained on how to minimize and detect beam misalignment and collimation failure since the most unacceptable results were observed from these tests.