Salary, terms and conditions would remain the same as Williams' current contract.
"As it has transpired, having leadership stability and certainty will be vitally important to both this organisation and to our district during these current uncertain times and post COVID-19," Chadwick said.
"I congratulate Geoff and also our councillors in approving his re-appointment."
Williams thanked elected members for their vote of confidence and said it was "an absolute privilege" to lead Rotorua Lakes Council and to be working with them and staff for the "betterment of the district".
"This is a great organisation and right now we are all in very uncertain times," he said.
"I have every confidence that you will see a strong response from this organisation. Nobody knows what things will look like when we emerge, but I do know that this organisation will be ready to stand up again ... and will look to maximise opportunities to recapture what's special about Rotorua to ensure a strong future for the district."
The recruitment process, which facilitator Greg Tims said was "rigorous", shortlisted three applicants for interview.
"We had a high calibre of applicants, which included people already in chief executive roles," Tims said.
All interviewees underwent the same process, he said, so there was the same opportunity to highlight their skills and experience.