Purpose The aim of this study was to evaluate the intra- and inter-rater reliability of static and dynamic postures in the transverse abdominal muscles (TrA) using manual testing and velcro strap of the transducer in B-mode ultrasonography (US). Methods Twenty-three healthy participants were evaluated using two different measurement methods by two raters within one day and on three different days. They were implemented with abdominal drawing-in maneuver (ADIM) with lying, ball-sitting, and hand-on-knee positions using manual testing or Velcro strap of the transducer. Results There were statistically significant differences in TrA between ADIM with lying and hand-on-knee positions (p<0.05). Intra-class correlation coefficient (ICC) values of the transducer with Velcro strap for inter-rater and intra-rater reliability were higher on ADIM with lying (0.94 and 0.96), ball-sitting (0.87 and 0.88), and hand-on-knee (0.86 and 0.91) positions compared to manual testing. Conclusion Our results suggest that hand-on-knee exercise affects TrA contraction and has higher reliability using the transducer with a velcro strap.