The skeletal muscle T-tubule system, a specialized membrane domain essential for coordinated muscle contraction, shows dysmorphology in a number of genetically inherited muscle diseases. However, in the absence of genetically tractable systems the mechanisms involved in T-tubule formation are unknown. Here, we have used the optically transparent zebrafish system to probe T-tubule development in vivo. By combining live imaging with three-dimensional electron microscopy, quantitative overexpression screening and genetic knockout models, we define a new endocytic capture model involving i) formation of dynamic endocytic tubules at transient nucleation sites on the sarcolemma ii) stabilization by myofibrils/sarcoplasmic reticulum and iii) delivery of membrane from the recycling endosome and Golgi complex.