Aims: Postnatal hippocampal development is a crucial period for neuronal maturation and pathway organization, characterized by morphological changes and an increased number of ion channels in the membrane. While anatomical and immunohistochemical studies inform neuronal pathway maturation, direct electrophysiological recordings are needed to assess intrinsic firing properties and functional synaptic activity. Previous studies primarily have focused on rats, but utilizing novel tools tailored for mouse models with electrophysiological recordings offers deeper insights into postnatal development mechanisms. Sex differences also may be important. The aim of this study was to examine the intrinsic firing properties of hippocampal pyramidal CA1 neurons during postnatal development. Methods: In this study, we used wild-type mice (5 to 21 postnatal days), males and females, and employed the whole-cell patch-clamp technique. The firing properties were evaluated as a steepness of frequency-current (f-I) relation, presenting how neurons integrate inputs and encode outputs through action potential frequency. Additionally, the rate of spike frequency adaptation was evaluated. Results: Our findings show a significant decrease in the steepness of f-I relation throughout development in males and females before and after spike frequency adaptation. The steepness of f-I relation significantly decreased during spike adaptation in all groups tested. The ratio of adaptation did not change with age. Furthermore, no notable differences were observed between male and female groups for parameters tested. Conclusions: Our findings reveal that the precision of CA1 neuron output control increases during development.