Background Ankylosing spondylitis (AS) is a chronic systemic inflammatory disease that can progressively restrict spinal mobility. Objective This study aimed to investigate how smoking cessation by AS patients affects disease activity and their psychological state, physical mobility, lung function, and quality of life. Materials and Methods This was a longitudinal, single-blind, controlled, and observational study on 92 AS patients. Pulmonary function test, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index, Bath Ankylosing Spondylitis Metrology Index, chest expansion, Short-Form 36, and Ankylosing Spondylitis Quality of Life were evaluated. The patients were divided into smokers (group 1 = 54) and nonsmokers (group 2 = 38). The smokers were divided further into subgroups of those who quit smoking (group 1a = 17) and those who did not (group 1b = 37). Groups 1a and 1b patients were compared in terms of their baseline data and data 6 months after smoking cessation. In addition, group 1a patients' baseline data and data 6 months after smoking cessation were compared statistically. Results There was no statistically significant difference between groups 1a and 1b after 6 months in terms of the evaluated parameters, except for BASDAI. Bath Ankylosing Spondylitis Disease Activity Index was significantly lower in group 1a than group 1b (p = 0.02), indicating that. When the baseline data and data after 6 months of group 1a were compared, a significant improvement was found in BASDAI (p = 0.001), Bath Ankylosing Spondylitis Functional Index (p = 0.001), chest expansion (p = 0.001), ankylosing spondylitis quality of life (p = 0.003), and subparameters physical function (p = 0.015), physical role strength (p = 0.05), power/live/vitality (p = 0.025), social functioning (p = 0.039), pain (p = 0.036), and general health perception (p = 0.05) of Short-Form 36, as well as forced expiratory volume in the first second (p = 0.003) and forced vital capacity (p = 0.007). Conclusions We observed significant improvements in disease activity, physical mobility, and quality of life in AS patients who quit smoking.