Traveling-wave tube (TWT) performance is sensibly affected by fabrication tolerances. An accurate yield evaluation and comprehension of the factors that contribute to yield degradation is fundamental to avoid excess costs in the fabrication process. In this paper, a procedure to evaluate and improve the yield of multisection helix TWTs in the design phase will be proposed, assuming a small-signal gain performance goal as the design target. An extended set of fabrication parameters is considered to provide a reliable estimate of the manufacturing tolerance effect on the final result. The introduction of yield sensitivity histograms together with cathode voltage adjustment demonstrates a relevant TWT yield improvement, together with indications on which fabrication step requires higher accuracy.