Born January 1, 1964, Umahi is the son of Elder Joseph Umahi Nwaze and Margette Umahi of Umunaga. Umahi received his secondary education from Ishiagu High School and the Government Secondary School of Afikpo before entering the Enugu State University of Science and Technology in 1982. He graduated in 1987 with a Bachelor of Science Degree in Civil Engineering.
In 1990, he co-founded Norman Engineering and Construction Nig. Limited with Ombo Isokarari, serving as its general manager until 1993. Until 2011, he served as chairman and CEO of Brass Engineering & Construction Nig. Ltd., Focus Investment Nig. Ltd., and Osborn La Palm Royal Resort Ltd.