A sample of kinematically identified K+->pi(+)pi(0) decays obtained with the E949 detector was used to search for the helicity-suppressed decay pi(0)->nu(v) over bar(v) over bar resulting in an upper limit of 2.7x10(-7) at 90% confidence level. The upper limit is also applicable to pi(0) decays into unknown weakly-interacting particles.
