Korean stop contrasts (lenis, fortis, and aspirated) have been phonetically differentiated by Voice Onset Time (VOT), but with a tonogenetic sound change in progress, the role of fundamental frequency (F0) has been amplified for distinguishing between Korean stop contrasts with the loss of VOT differentiation in young adults’ production. The present study explores how F0 is perceptually acquired and how it phonetically operates in toddler speech in relation to Korean stop contrasts according to age. In order to determine the relationship between F0 developmental patterns and age in child stop production, this study uses a quantitative acoustic model to examine the word-initial stop productions of 58 Korean monolingual children aged 20 to 47 months. The production experiment confirmed that VOT is useful for distinguishing fortis stops, but F0 is required for distinguishing between lenis and aspirated stops, and this tendency is significantly related to age. As F0 becomes a determinant acoustic parameter for articulatory distinction, the role of F0 in perceptual distinction was investigated through a perceptual identification test with the F0 continuum. Children were provided with selected lenis-aspirated pairs of images in which they would point to one or the other image in response to given synthetic sounds with different F0 values. This allowed us to observe how phonetic boundaries in the F0 dimension for aspirated stops change with age. A comparative analysis between children’s production and perception of F0 indicates that articulatory skills depend on perceived F0 differences depending on the phonemic categories. Additionally, the analysis indicates that once F0 is acquired, VOT differentiation diminishes for distinction between lenis and aspirated stops, and this trade-off between VOT and F0 would occur around the age of 3 years. These findings suggest that phonemic categorization of lenis and aspirated stops should be processed in the F0 dimension and that phonemic processing in perceptual acoustic space is directly linked to phonetic discrimination between the non-fortis stops in production. This study provides experimental evidence for understanding a developmental trajectory of F0 as an acoustic cue for native phonological contrasts.