Background and Purpose: Voltage-gated Na+ channels are critical therapeutic targets of anti-seizure medications. The structurally related compounds carbamazepine (CBZ), oxcarbazepine (OXC), eslicarbazepine acetate (ESL), and S-licacarbazepine (S-Lic) of the dibenzazepine family are generally presumed to exert similar effects; however, a comparative analysis under identical conditions is lacking. Here, we rigorously compared their effects on biophysical properties of Na+ channels and effects on neuronal networks. Experimental Approach: 293T cells stably expressing Nav1.2 channels were employed to assess biophysical profiles using whole-cell patch clamp techniques. Additionally, the impact on neuronal networks in primary cortical neurons was evaluated using microelectrode array recordings. Key Results: CBZ and OXC exhibited similar effects on voltage-dependent fast inactivation and recovery from inactivation. ESL and S-Lic also influenced fast inactivation, but their effects were less pronounced than those observed with CBZ. Notably, S-Lic exhibited comparatively small effects on use-dependent block. For all compounds, effects on slow inactivation were subtle. With regards to neuronal network activity, CBZ, OXC, and ESL induced substantial changes in spiking, bursting, and synchrony. S-Lic elicited significant and selective effects on network synchrony without effects on other parameters. Lacosamide elicited significant effects on bursting. Conclusion and Implication: CBZ, OXC and ESL exhibited similar activity profiles on properties of Nav1.2 channels and neuronal networks. The structurally similar S-Lic showed significantly less use-dependent blocking effect, and a selective effect on distributed network bursts. These results emphasize that structurally similar dibenzazepine anti-seizure medications can exhibit substantial differences in activity on the ion channel and network level.