Introduction: The knowledge of pre-existing medical illnesses and their follow up status among active pulmonary tuberculosis (PTB) subjects can help in tuberculosis (TB) control programme. The aims of our study were to examine: the prevalence of pre-existing chronic medical illnesses, the follow up status of known pre-existing co-morbid and to distinguish between diagnosed and undiagnosed preexisting tuberculosis related chronic medical illnesses among our active PTB subjects. Methods: We conducted a retrospective review of demographic and clinical data of active PTB subjects that were diagnosed between January 2015 and June 2017 in the district of Manjung, Perak, Malaysia. Among the 302 TB clinical notes reviewed, 253 patients were included. Subjects below the age of 18 years and whose follow up centres for their medical illnesses that were located outside of Manjung were excluded. Demographic and clinical data were collected using pre-tested data collection form by trained investigators. The data was analysed using SPSS Version 20.0. Results: We identified diabetes mellitus as the most prevalent pre-existing co-morbid (77 cases) and almost 90% (68 cases) of these diabetic subjects were diagnosed prior to active PTB diagnosis. This was followed by Human Immunodeficiency Virus and Hepatitis C infection which accounted for 12.0% (30 cases) of the study populations. Among 132 subjects who had pre-existing chronic medical illnesses, only 74 subjects (29%) were under regular follow up at healthcare facilities in Manjung prior to PTB diagnosis. Conclusion: Overall, our research provides evidence on the existence of wide variation of clinical background among active PTB subjects.