Background- Patients with Human Immunodeficiency Virus (HIV) have higher risk of developing tuberculosis (TB) compared to uninfected individuals. The World Health Organisation (WHO) recommends fixed dose combinations (FDC) of antibiotics, anti-tubercular, and vitamins to treat latent TB. Multiple drugs for minimum 6 months are needed to effectively treat active TB. Incorrect mono-therapy and non-adherence increases disease relapse, treatment failure, and drug resistance. FDCs containing 2+ anti-TB drugs improve adherence by reducing tablet count, preventing mono-therapy, aiding dose calculation, increasing acceptance, minimizing errors, and reducing pill burden. Methodology- A combination of Sulfamethoxazole and Trimethoprim (SMX-TMP) at concentrations of 8.3 μg/ml of SMX and ≥1.6 μg/ml of TMP has been effectively used in patients with extensively drug resistant (XDR) strains of Mycobacterium tuberculosis. Given the efficacy of SMX-TMP against XDR M. tuberculosis, this combination was preferred in the current study. Additionally, Isoniazid (INH) is effective against M. tuberculosis. However, treatment with INH can lead to a deficiency of the vitamin B6 called Pyridoxine (PY). To address this issue, 10 mg of Pyridoxine hydrochloride (PY-HCl) was added with each 100 mg dose of INH. The aim of this study is to formulate, optimize, and evaluate in vitro a new FDC using SMX, TMP and INH, PY HCl to treat co-infection of HIV and TB. Tablets were prepared with maize starch, povidone K30 (PVP K30), sodium lauryl sulphate (SLS), Starch1500, croscarmellose sodium (CCS), sodium starch glycolate (SSG), colloidal silicon dioxide (Aerosil), and magnesium stearate using the wet granulation method. Dissolution testing was performed in 0.1 N HCl for each tablet separately and also for the mixture of the three drugs, with quantification done using HPLC. Results - The optimized batch F8 showed satisfactory dissolution results for the FDC compared to the other formulation batches. Therefore, the FDC tablet containing 800mg SMX, 160mg TMP, 300mg INH and 25mg PY-HCl was successfully designed as compressed tablets meeting the final product specifications.