Westpac has 4500 employees in New Zealand and Fonterra more than 12,000.
Mr Miller said Westpac intended to roll the programme out to all its branches.
"We have been doing it informally for about five years and in October we formalised it," he said.
"We wanted to do the right thing to help our employees [if they experience domestic violence]."
"We want to make the workplace a catalyst for change."
Fonterra is using the programme to create a safe and supportive environment at work, while also enabling staff affected by family violence to take up to 10 days of additional paid leave per year for matters relating to it.
Managing director people and culture Joanne Fair said businesses had a huge role to play in tackling one of New Zealand's biggest social issues.
"We want to play our part in getting our people the help they need, as the workplace is often a safe place from violence at home," she said.
The programme encouraged staff to talk about family violence and ensured they knew help was available if needed.
"If we can make a difference in the lives of victims, supporters of victims and users of family violence who want to change, then we'll also make a difference for their families and the communities they live in," she said.
Southland Farm Source regional head Mark Robinson said family violence could affect anyone, no matter their gender, age, education, background or social status.
"The effects are likely to carry over into the work environment," he said.
"It's really important we make that environment a safe place to talk about family violence and help people get the support they need."