Background: Chronic low back pain (CLBP) is associated with trunk and lower extremity muscle weakness. Kneeling squat (KS) is a hip-focused exercise commonly used in the activities of daily living. However, research on trunk and lower extremity muscle activity across movement phases (ascending, holding, and descending) during KS remains limited and warrants further investigation. Objects: To determine the muscle activity of transversus abdominis/internal oblique (TrA/IO), erector spinae, gluteus maximus (Gmax), gluteus medius (Gmed), rectus femoris (RF) in the contraction phases of KS in individuals with CLBP. Methods: Surface electromyography data were recorded during KS across the ascending, holding, and descending phases on the side with CLBP. A 60-bit metronome was used to control the exercise speed. Results: The muscle activity of the TrA/IO was significantly higher during the holding phase than during the ascending and descending phases. The Gmax and Gmed were significantly higher during the holding phase than during the descending phase, whereas, RF was significantly higher during the ascending phase than during the holding and descending phases. Conclusion: The holding phase of KS may be recommended as a trunk and lower extremity exercise to increase in TrA/IO, Gmax, and Gmed muscle activity. Additionally, the ascending phase activates RF muscle in individuals with CLBP.