Olfaction is considered the evolutionarily oldest sense, which together with somatosensation, is crucial for neonatal well-being before audition and vision start engaging the brain. Using anatomical and functional approaches, we reveal that olfactory-driven activity propagates to a large part of the cortex during the first postnatal week, and enhances whisker-evoked activation of primary whisker somatosensory cortex (wS1). This effect disappears in adult mice, due to the loss of neonatal excitatory connectivity from olfactory cortex to wS1. By performing developmental olfactory-deprivation and adult electrophysiological and behavioral experiments, we find a key transient regulation of olfactory information for the development of wS1 sensory-driven dynamics and somatosensation. Our work has uncovered a cross-modal critical window for somatosensory functional maturation determined by olfaction.