Mild traumatic brain injuries (mTBI) comprise roughly 80% of all brain injuries and represent the majority of TBI patients seen in hospitals. mTBI can result in a wide-range of cognitive deficits and patients often develop co-morbid psychological disorders post-injury. The current study identified whether co-morbid psychological diagnoses are associated with specific patterns of cognitive deficits in 232 mTBI patients, aged 17-78 years, by means of cluster analyses. The presence of a co-morbid adjustment disorder was related to deficits in mental flexibility and attention, and the presence of a pain disorder was associated with deficits in abstract reasoning. Also, the presence of multiple co-morbid diagnoses was related to deficits in visual-spatial construction, abstract reasoning, mental flexibility and attention. Demographic variables, such as greater months since injury and fewer years of education, were also linked to deficits in cognitive functioning. This study highlights the influence of psychological diagnoses on cognitive test performance and provides support for the need to address co-morbid diagnoses during rehabilitation.