Background: Core stabilization exercises are widely used to improve trunk stability, balance, and functional movement by enhancing the activation and endurance of deep trunk muscles such as the transversus abdominis (TrA). However, evidence comparing the effects of sling-based unstable surface training and mat-based stable surface training remains limited. Objects: To investigate the effects of mat based core stabilization exercises and sling based unstable surface core stabilization exercises on transversus abdominis thickness and core endurance. Methods: Forty-six healthy adults were randomly assigned to a mat exercise group (MEG, n=23) or a mat with sling exercise group (MSEG, n=23). Both groups performed 30-minute core stabilization exercises twice per week for four weeks. TrA thickness was measured using ultrasonography (SONON 300L), and core endurance was evaluated using the Bourban test for the anterior muscle chain. Results: Both groups showed significant increases in transversus abdominis thickness (MEG: P<.05; MSEG: P<.00) and core endurance (P<.00) after the intervention. However, no statistically significant differences were found between the two groups in post-intervention TrA thickness or Bourban test. Conclusion: Both mat based and sling based core stabilization exercises effectively enhanced TrA thickness and core endurance in healthy adults.