AbstractFunctional role of lingual nerve in breastfeeding was investigated in rat pups during the suckling period. DiI, a postmortem neuronal tracer, was used to confirm the immature lingual nerve (LN) responsible for tongue sensation and resulted in successful fiber labeling anterogradely to the tongue, which showed different distribution patterns from fiber labeling derived from the hypoglossal nerve. Unilaterally LN‐injured pups did not show suckling disturbance with absence of any shortening (P11 pups: 559 ± 16 s; 105% of the control value) in nipple attachment time and the survival rate remained high (P11: 100%). Bilaterally LN‐injured pups showed suckling disturbance with marked shortening (P11 pups: 220 ± 54 s; 42% of the control value) in nipple attachment time and a low survival rate (P1: 33%; P11: 41%). Bilaterally infraorbital nerve‐injured or bilaterally bulbectomized pups did not show any nipple attachment at all and there were no survivors, confirming the crucial roles of upper lip sensation and olfaction in suckling. Based on these findings, we conclude that tongue sensation is very important, but not essential for suckling.