Ovine Respiratory Complex is a multifactorial disease involving interactions between pathogens, host factors, and environmental conditions. This study investigated associations between selected bacterial agents, including Mycoplasma ovipneumoniae infection and members of the Pasteurellaceae family, and clinical, auscultatory, ultrasonographic, and post-mortem findings in Lacaune fattening lambs. A total of 80 animals were evaluated using clinical examination, thoracic auscultation, ultrasonography, post-mortem assessment, bacteriological culture, and quantitative PCR (qPCR) for Mycoplasma ovipneumoniae. Associations between microbial detection and disease severity scores were analyzed. Mycoplasma ovipneumoniae was the most frequently detected organism (50%), followed by Pasteurella multocida (32.9%) and Trueperella pyogenes (27.8%). Detection of specific microorganisms was more frequently observed in animals with increased disease severity across multiple diagnostic modalities. Coinfection was identified in 60.8% of animals and was significantly associated with increased severity according to clinical, auscultatory, ultrasonographic, and post-mortem scores. These findings underscore the polymicrobial nature of ORC and emphasise the necessity of employing complementary diagnostic approaches for disease evaluation.