A W‐band low‐cost and high output power tripler based on a substrate integrated suspended line (SISL) platform is presented in this paper. An accurate three‐dimensional electromagnetic model is established to characterize the high‐frequency parasitic effect of diodes, and the field‐circuit cosimulation method is employed to design the tripler. A SISL‐WR10 transition is designed and added in the output port to facilitate the test, and it also functions as a W‐band bandpass filter (BPF) to output the third harmonic, which avoids insertion loss caused by an additional BPF and makes the tripler more compact. The whole circuit of the tripler is fabricated on FR4 substrates, and it is self packaged. The measured results show that with 22 dBm input power, the tripler achieves 0–4.46 dBm output power from 75 to 106 GHz.