We designed, synthesized, and tested twenty-six novel tetrahydroisoquinoline carbohydrazide compounds for their anti-mycobacterial activity. Utilizing mass spectrometry, ¹H NMR, ¹³C NMR, and elemental analysis, all the synthesized derivative structures were confirmed. The final analogs were tested for their ability to inhibit Mycobacterium tuberculosis (Mtb). The Mtb inhibitory activity outcomes varied from 0.78 to 25 μg mL⁻¹. Among all the investigated analogues, compounds NFT-12, NFT-19, and NFT-20 exhibited substantial activity with a MIC of 0.78 μg mL⁻¹ against Mtb H37Rv. Furthermore, the NFT-11 compound showed excellent activity with a MIC of 1.56 μg mL⁻¹. The majority of the compounds showed very good activity compared to the standard drug rifampicin (MIC 3.12 μg mL⁻¹). The most active compounds, NFT-12, NFT-19, and NFT-20, demonstrated selectivity over the normal human embryonic kidney cell line (HEK293T) with a selectivity index of >40. To determine whether the designed compounds exhibit synergistic effects or not, drug–inhibitor combination studies were carried out for the most active compounds using the standard drugs isoniazid, rifampicin, ciprofloxacin, and streptomycin. The improvement in pharmacological activities (x/y coefficients) demonstrates the effectiveness of the compounds NFT-12, NFT-19, and NFT-20 with isoniazid. The expected binding site of the test ligand at the active site of the chosen target proteins was determined using molecular docking studies. The most active compounds NFT-12, NFT-19, and NFT-20 were used in the docking experiments to determine the binding pattern at the active site with the Mycobacterium tuberculosis InhA (PDB ID: 4OHU, 1.60 Å).