The changes followed the resignations from Cabinet of Hekia Parata and Murray McCully.
"I'm grateful to the Prime Minister for having confidence in me and that he has recognised that, but this was only possible due to the support I get from the Rotorua electorate," Mr McClay said.
"It gives me the opportunity to work hard and continue to deliver for the people of Rotorua as well as make the case on the world stage for better access to important markets around the world.
"I was at a Rotary club listening to a girl from Rotorua Girls High School giving a speech about racism and war and I was not expecting it at all."
He said he would be in his Rotorua electorate this week and would return to Wellington on Friday to farewell Mr McCully.
Mr McClay said the region now had six MPs in Cabinet who were based in and around the Bay of Plenty - himself, Tauranga MP Simon Bridges, East Coast MP Anne Tolley, Taupo MP Louise Upston, Coromandel MP Scott Simpson and Mr Flavell.
Mr Bridges was appointed Leader of the House and retained his positions as Minister for Economic Development, Minister of Transport and Minister for Communications.
The new ministers will be sworn in next Tuesday and the new Cabinet will hold its first meeting on May 8.