Magnetoencephalography with optically pumped magnetometers (OPM-MEG) has become a focus of research. Signal sources can be estimated using OPM-MEG, where the sources are approximated as current dipoles, such as those associated with sensory evoked fields (SEFs). However, previous studies have typically used around 100 OPM-MEG sensors within high-performance magnetically shielded rooms (MSR) with active shielding. In this study, we aimed to develop OPM-MEG with a reduced number of sensors in a moderate MSR. To minimize the effects of magnetic field gradients in this environment, we fixed the sensor helmet to the MSR. Either 48 or 16 OPM-MEG sensors were used, depending on the configuration. Using these setups, we measured SEFs and compared the estimated locations of signal sources with those obtained from a conventional 306-channel MEG with a superconducting quantum interference device (SQUID-MEG). Five adults (one woman, four men), aged 33.6 ± 8.02 years (mean ± SD) participated in this experiment. To co-register the sensor positions to the participant’s head coordinates, head position indicator coils were used in the 48-channel configuration, whereas reference points embedded in the sensor helmet were used in the 16-channel configuration. Signal source estimation was performed using minimum norm estimation with dynamic statistical parametric mapping on a 5-mm grid-based volume model. SEF peak latencies were determined at the peaks of the global field power around 20 ms (N20m) from the stimulus onset. The SEF signal source locations were defined as the voxel coordinates with the highest dSPM values within the somatosensory or motor cortex at the SEF peak latencies. The SEF signal source locations estimated by the 48-channel and 16-channel OPM-MEG differed from those estimated using SQUID-MEG by 10.81 ± 5.42 mm and 11.95 ± 4.66 mm (mean ± SD), respectively. Based on previous studies comparing source estimates across multiple SQUID-MEGs, this level of discrepancy is considered acceptable. These results suggest that the source locations of SEFs can be estimated reliably even with a 16-channel OPM-MEG operating in a moderate MSR.