The study investigated the effects of six-week progressive strengthening exercise on pain and functional capacity among patients with chronic low back pain. Forty-two men and women patients within the age range of 25-60 years recruited from Osun State Hospital (Asubiaro) and Lautech Teaching Hospital all from Osogbo Metropolis were used for the study. A pretest-Posttest design was adopted while purposive and total enumeration sampling techniques was used to select the participants. The Instrument used for data collection were Visual Analogue Scale (VAS) and Oswestry Low Back Pain Disability Questionnaire. The result from this study indicated a significant low pain and functional inability respectively after a six-week progressive strengthening exercise among patients. This means that six weeks progressive strengthening exercise is effective in reducing pain and increasing functional capacity among patients with low back pain and therefore recommended as intervention in the management of chronic low back pain.