Before becoming the mayor of Surabaya, Widjaja served as chairman of the Malang city council. He was sworn in as Mayor on 27 January 1979.[2] Under his own admission, there was not a lot of physical development within the city in the first two years of his tenure, partly due to lack of funding in the municipal budget. For a number of development projects of the villages within the city's boundaries, funding was provided by both the municipal government and local contributions.[3] He was replaced by Poernomo Kasidi on 20 June 1984.[4]
He died in his Surabaya home on 15 April 1985 from a heart attack.[1] He was buried at the 10 November 1945 Heroes' Cemetery in Surabaya.[5]
^"Drs Muhadji Widjaja, Walikotamadya Baru Surabaya". Kompas (in Indonesian). 30 January 1979. Retrieved 8 October 2021. Drs. Moehadji Widjaja (48 tahun) dengan jabatan terakhir Ketua DPRD Kotamadya Malang, dilantik menjadi Walikotamadya/KDH Tingkat II Surabaya tanggal 27 Januari