Fluidized beds are found in the energy production industry, it is important to know their hydrodynamic conditions, such as local gas holdup or volumetric gas fraction, for effective operation. Local measurement probes have been used to measure local gas holdup. Although the probes are typically as small as possible to mitigate their influence on the local conditions, the invasive nature of this measurement technique has the potential to alter the fluidized bed behavior. This study used a noninvasive measurement technique, X-ray computed tomography (CT) imaging, to determine the local time-average gas holdup everywhere within a 10.2 cm diameter fluidized bed filled with 500-600 μm glass beads in which simulated probes were inserted. Three different probe tips (pointed, rounded, and flat) and two different orientations (horizontal and vertical) were investigated at four different bed heights and two different fluidization velocities. The results show increases in local time-average gas holdup when the probes are present, but the scale of the effects was dependent upon the height at which the probes were placed; the lower the probe within the fluidized bed, the larger the local effects. Probe tip geometry showed no differences in the local gas holdup. Probe orientation was an important factor though, with the horizontal orientation showing a sustained increase in gas holdup values farther upstream from the probe. The two different flow rates used in this study (1.5Umf and 3Umf, where Umf is the minimum fluidization velocity) also showed differences in the amount of variation in gas holdup, but the trends were inconsistent.