The direct delivery of antibiotics to the lung has been considered an effective approach 19 to treat pulmonary tuberculosis, which represents approximately 80% of total cases. In 20 this sense, this work aimed at producing inhalable chitosan microparticles simultaneously associating isoniazid and rifabutin, for an application in pulmonary tuberculosis therapy. 22 Spray-dried chitosan microparticles were obtained with adequate flow properties for deep 23 lung delivery (aerodynamic diameter of 4 µm) and high drug association efficiencies 24 (93% for isoniazid and 99% for rifabutin). The highest concentration of microparticles 25 that was tested (1 mg/mL) decreased the viability of macrophage-differentiated THP-1 26 cells to around 60% after 24 h exposure, although no deleterious effect was observed in 27 human alveolar epithelial (A549) cells. The release of LDH was, however, increased in 28 both cells. Chitosan microparticles further evidenced capacity to activate macrophage-29 like cells, inducing cytokine secretion well above basal levels. Moreover, the propensity 30 of macrophages to internalise microparticles was demonstrated, with uptake levels over 31 90%. Chitosan microparticles also inhibited bacterial growth by 96%, demonstrating that 32 the microencapsulation preserved drug antibacterial activity in vitro. Overall, the obtained 33 data suggest the potential of chitosan microparticles systems for inhalable lung 34 tuberculosis therapy.