Governor Vajubhai R. Vala administered the oath of office to Krishnappa at Raj Bhavan in the presence of Chief Minister Siddaramaiah, some of his cabinet colleagues and senior officials.
The 61-year-old two-time legislator from Vijayanagar in the city's southwest suburb belongs to the politically dominant Vokkaliga community.
He declared assets valued at Rs 147 crore to the Election Commission when the last assembly elections were held in April-May 2013.
Krishnappa's eldest son Priya Krishna is also a Congress lawmaker with declared assets valued at a whopping Rs 910 crore.
According to party sources, Krishnappa is likely to get housing portfolio that was held by rebel Kannada actor-turned lawmaker M.H. Ambarish till he was dropped from the 40-month-old government on June 19 with 13 other ministers.
Krishnappa's induction takes the ministry's strength to 33, including the Chief Minister, 29 with cabinet rank and four ministers of state.
In a related development, on Siddaramaiah's recommendation, the Governor has promoted Minister of state for Animal Husbandry, Fisheries and Horticulture A. Manju and Minister of State for Mines and Geology Vinay Kukarni to cabinet rank.
Of the 34-member cabinet, one post is vacant following the resignation of K.J. George as Bengaluru Development Minister on July 18 after a court ordered police to file an FIR against him in connection with the alleged suicide of Mangaluru Deputy Superintendant of Police M.K. Ganapathi.