She said Nicholson brought to his new role more than 15 years of high-level management experience, including six and a half years as a member of Whanganui District Council's executive leadership team.
For the last four, he has held the role of chief operating officer.
Prior to his time in local government, Nicholson was a sergeant in the New Zealand Police and a team leader in the New Zealand Defence Force.
Collis said the district was built on strength and unity.
"Seven towns make up our district and each has its own identity and history but together we make up one strong district. Our towns respect each other and have each other's backs as we move forward and strive to make Tararua the best place in New Zealand to live."
On behalf of council staff, deputy chief executive Peter Wimsett and chief financial officer Raj Suppiah also extended welcomes.
"We are a council with good family values, but we do have our challenges," Wimsett said.
"This year our resilience has been tested through Covid-19 and a drought but we came through well and gained recognition for our efforts."
He told Nicholson it was a good time for him to join the council as many of its large projects had come to fruition, although there were more to come.
"The growth of the district has been huge and is now at the point we thought it would be at in 10 years time which does create challenges.
Suppiah agreed it was a good time for Nicholson to become part of the council.
"The underlying theme here is change. Change doesn't have positive connotations but to us change is good, change is progress, it keeps us relevant and we embrace the opportunities ahead of us."
McDouall said it was a special day for several reasons.
"Bryan went to school just up the road, he played rugby here and worked as a policeman here."
He said he first met Nicholson six years ago when he was part of the customer services team.
"He struck me as a person who looks for solutions. He de-escalates situations and tries to find a compromise. When these steps fail he is resolute."
He said it was a tribute to Nicholson that almost all members of the council's executive team had travelled from Whanganui for the welcome.
In reply, Nicholson thanked Collis for having the trust and confidence in him to appoint him to his new role.
"To the staff, I would say don't see this as a negative thing. It's a positive and I look forward to working with you all."
He said he also looked forward to working with the district's community boards.
Collis said she had every confidence in Nicholson's abilities to work with the council in what was an exciting time facing the district.
