Morphogenesis, the establishment of rudimentary organ structures, requires embryonic cells to generate forces and perform mechanical work to shape their tissues. Incorrect functioning of these force fields can lead to congenital malformations including neural tube defects. The understanding of these dynamic processes requires quantification and profiling of three-dimensional mechanics during evolving vertebrate morphogenesis, which is not tractable with current technology. We fabricated elastic spring-like force sensors with micron-level resolution directly into specific three-dimensional domains of the closing neural tubes of growing chicken embryos through intravital three-dimensional bioprinting. Integration of calibrated sensor readouts with computational mechanical modelling allows direct quantification of forces and work performed by embryonic tissues. The two halves of the closing neural tube at the embryonic midline reach over a hundred nano-Newton compression during neural fold apposition. Unexpectedly, diminishing pro-closure force by pharmacologically inhibiting Rho-associated kinase reveals active anti-closure forces which must depend on alternative mechanisms or tissue properties, and which progressively widen the neural tube. Pro-morphogenetic forces must therefore overcome anti-morphogenetic forces to achieve neural tube closure.