In this work, a broadband microstripline‐to‐waveguide (MSL‐to‐WG) transition has been presented for E‐band module applications. In order to extend its bandwidth (BW), extended ground (eGND) planes and patch‐type probe are designed and their dimension and structure are optimized. Compared to the ordinary transition using a simple electric probe (S‐probe), the optimized eGND plane on the dielectric substrate and triple‐patch probe enhance the operational BW of 56.4 and 71.7%, respectively. The designed transition on the low‐loss liquid crystal polymer (LCP) dielectric substrate was fabricated. Its measured operational BW for the reflection loss (S11) below −10 dB is over 28 GHz at all test frequencies from 67 to 95 GHz. The measured insertion loss of the fabricated transition can be analyzed as −1.45 and −1.59 dB per a transition at 70 and 80 GHz, respectively, considering the loss contribution of the cable adapter and waveguide transition. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1398–1401, 2016