Novel diagnostic tests hold promise for improving tuberculosis (TB) control, but their epidemiologic impact remains uncertain. Using data from the World Health Organization (2011–2012), we developed a transmission model to evaluate the deployment of 3 hypothetical TB diagnostic tests in Southeast Asia under idealized scenarios of implementation. We defined diagnostics by their sensitivity for smear-negative TB and proportion of patients testing positive who initiate therapy (“point-of-care amenability”), with tests of increasing point-of-care amenability having lower sensitivity. Implemented in the public sector (35% of care-seeking attempts), each novel test reduced TB incidence by 7%–9% (95% uncertainty range: 4%–13%) and mortality by 20%–22% (95% uncertainty range: 14%–27%) after 10 years. If also deployed in the private sector (65% of attempts), these tests reduced incidence by 13%–16%, whereas a perfect test (100% sensitivity and treatment initiation) reduced incidence by 20%. Annually detecting 20% of prevalent TB cases through targeted screening (70% smear-negative sensitivity, 85% treatment initiation) also reduced incidence by 19%. Sensitivity and point-of-care amenability are equally important considerations when developing novel diagnostic tests for TB. Novel diagnostics can substantially reduce TB incidence and mortality in Southeast Asia but are unlikely to transform TB control unless they are deployed actively and in the private sector.