(1) Background: Inflammatory processes in the thoracolumbar fascia (TLF) lead to thickening, compaction, and fibrosis and are thought to contribute to the development of nonspecific low back pain (nLBP). The blood flow (BF) of fascial tissue may play a critical role in this process, as it may promote hypoxia-induced inflammation. The primary objective of the study was to examine the immediate effects of a set of myofascial release (MFR) techniques on the BF of lumbar myofascial tissue. The secondary objectives were to evaluate the influence of TLF morphology (TLFM), physical activity (PA), and body mass index (BMI) on these parameters and their correlations with each other. (2) Methods: This study was a single-blind, randomized, placebo-controlled trial. Thirty pain-free subjects (40.5 ± 14.1 years) were randomly assigned to two groups treated with MFR or a placebo intervention. Correlations between PA, BMI, and TLFM were calculated at baseline. The effects of MFR and TLFM on BF (measured with white light and laser Doppler spectroscopy) were determined. (3) Results: The MFR group had a significant increase in BF after treatment (31.6%) and at follow-up (48.7%) compared with the placebo group. BF was significantly different between disorganized and organized TLFM (p < 0.0001). There were strong correlations between PA (r = -0.648), PA (d = 0.681), BMI (r = -0.798), and TLFM. (4) Conclusions: Impaired blood flow could lead to hypoxia-induced inflammation, possibly resulting in pain and impaired proprioceptive function, thereby likely contributing to the development of nLBP. Fascial restrictions of blood vessels and free nerve endings, which are likely associated with TLFM, could be positively affected by the intervention in this study.