Background: Rheumatic mitral stenosis (MS) is associated with progressive impairment of left atrial (LA) mechanical functions. This study was conducted to assess the acute impact of Balloon Mitral Valvotomy (BMV) on these functions. Methods: This single centre observational study included 25 patients with severe MS (aged 34.1 ± 7.1 years, with mean mitral valve area of 0.74 ± 0.13 cm²), in sinus rhythm, who underwent successful BMV at our hospital. Phasic LA volumes (Vmax: maximal LA volume, Vmin: minimal LA volume, and Vp: LA volume at the onset of P-wave) were measured by modified Simpson’s method. Parameters of LA reservoir function i.e. LA total emptying fraction (LATEF) and LA expansion index (LAEI); conduit function i.e. LA passive emptying fraction (LAPEF); and pump function i.e. LA active emptying fraction (LAAEF) were calculated from these volumes. All these parameters were evaluated before and 24-48 hours after BMV. Results: Successful BMV led to significant reduction in Vmax (p < 0.001), Vmin (p < 0.001), and Vp (p < 0.001). There was a significant increase in LATEF (p= 0.001) and LAEI (p= 0.002). LAPEF increased insignificantly (p= 0.057), while there was no significant change in LAAEF (p =0.127) after BMV. Conclusion: Successful BMV leads to early improvement in left atrial reservoir and conduit functions, without significantly affecting left atrial pump function. Whether these acute changes translate into long term left atrial reverse remodelling and clinical benefits thereof needs to be established by further studies.