"It is a very special occasion. You walk in there and find your seat with your name on it ... It really is very humbling."
While Parliament officially opens today Mr Muller said the work began now.
"I am on the select committees for social services and also local government and the environment," he said.
"I'm really delighted with that and I am looking forward to getting stuck in."
He said he was not nervous during yesterday's proceedings but was "thrilled" to be there.
Mr Mitchell said the day went "very, very well".
He described it as a neat feeling and pretty surreal.
"I did the affirmation and I had my father, sister and wife in the public gallery," he said.
"I have more family coming for my maiden speech, which will be on Thursday."
Mr Mitchell said he was due to find out what his portfolios would be in the next few days.
"I've also got our local issues which I will be fighting for."
Meanwhile, Mr Mitchell will be returning to Tauranga in the next few weeks to give his final address to the city council as he formally steps down as a city councillor.
Yesterday's proceedings began with a proclamation on behalf of Governor General Sir Jerry Mataparae read by Chief Justice Dame Sian Elias.
Accompanying her in her duties as Royal Commissioner were President of the Court of Appeal Justice Ellen France, and Chief Judge of the High Court Helen Winkelmann.
One hundred and nineteen of Parliament's 121 MPs were sworn in by Clerk of the House Mary Harris with Foreign Minister Murray McCully and Green MP Julie Anne Genter absent.
David Carter was re-elected Speaker.
Timeline
• General election was held on September 20.
• Cabinet members were sworn in on October 8.
• Members of Parliament were sworn in yesterday.
• Parliament will officially open today.
- Additional reporting NZME.