Activity of the insular cortex had been consistently suggested to be related with chronic pain. Of the sub-regions in the insular cortex, the posterior insular cortex (pIC) receives inputs from brain regions that receive primary sensory inputs. Anatomical changes of the pIC were reported in neuropathic pain conditions. However, how the activity of pIC neurons may be related with neuropathic pain remain to be investigated. We, therefore, investigated the role of pIC pyramidal neurons and neuropathic pain using optogenetics and fiberphotometry using male mice. We found that inhibiting the activity of pIC pyramidal neurons slightly ameliorated spared-nerve injury (SNI) induced reduction in mechanical nociceptive thresholds. The activity of the pIC pyramidal neurons, measured with fiberphotometry, around von Frey filament stimulation did not differ between the SNI and sham surgery groups. Overall, the activity of pyramidal neurons in the pIC region we investigated had a weak relationship with the SNI induced lowering of pain thresholds.