Caecilians are elongate and limbless amphibians. Except one aquatic family, they all have an at least partially fossorial lifestyle. It has been suggested that they evolved sturdy compact skulls with fusion of ancestrally separate bones and tight sutures as an adaptation for head-first burrowing. Although their cranial osteology is well described, relationships between form and function remain poorly understood. In this study, we report data on in vivo burrowing forces for more than 120 specimens belonging to 13 different species. Over 80 caecilians were µCT-scanned and their skulls segmented. Using fixed and semi-sliding anatomical landmarks, we performed 3D geometric morphometrics to quantify skull variability across species. Finally, using correlation tests, linear models and two-blocks partial least squares, we investigated the relationships between the overall cranial shape and in vivo burrowing force in caecilians. Surprisingly, results show that despite differences in the head morphology across species, there is no relation between overall skull shape and this particular measure of burrowing performance. Although a phylogenetic signal may partly obscure the results, our conclusions join previous studies using biomechanical models and suggest that any differences in their degree of fossoriality are not driving the correlated adaptive evolution of head shape and maximal burrowing force. As the cranium has multiple functions such as feeding, and houses major sensory organs, or respiratory systems, further studies are needed to fully understand the selective pressures shaping the evolution of skull form.