The money will be available for councils and housing associations to improve homes, as well as creating jobs and training opportunities.
There is a five year target for bringing 200,000 social homes up to quality and safety standards.
But Plaid Cymru said there was no "additional money" in the announcement.
Improvement work could include replacing boilers to new kitchens and bathrooms.
More than two thirds of social housing in Wales - nearly 150,000 homes - meet the 2020 quality target.
Housing minister Lesley Griffiths has already signalled her intention to end right to buy in Wales to prevent the loss of local authority housing stock.
Ms Griffiths said: "Investment in people's homes has a far reaching impact - it is vital in improving the nation's health and creating jobs and training opportunities."
She added the Welsh government was also investing more than £400m in affordable homes.
However, Plaid Cymru housing spokesperson Jocelyn Davies said the £100m  cash announced on Tuesday was simply "money that is distributed every year to bring social housing up to standard".
More than £100m is to be spent on improving Wales' stock of social housing, the Welsh government has announced.