The government is restoring almost $2 million in funding to the Growing Up in New Zealand study.
The University of Auckland longitudinal study looks at the health and development of almost 7000 children, who were born in 2009 or 2010.
They will be followed until they turn at least 21.
But a funding cut under the previous National government meant the sample size had to be cut back to 2000.
Minister of Social Development Carmel Sepuloni said restoring the study to its original sample size would allow for more detailed analysis of different ethnic groups, such as Māori and Pacific people.
The children taking part in the study are now eight-years-old and researchers are in the field doing interviews for the latest data collection wave.
Since the study began in 2008, more than 90,000 interviews have been carried out and more than 50 million pieces of data have been collected, Ms Sepuloni said.
"Information from the study has provided insights into a diverse range of areas such as paid parental leave, immunisation, family housing and mobility, household safety, participation in Early Childhood Education and pre- and post-natal depression among fathers," she said.
Findings from the study, and further research done with anonymised data from it, will help inform which services and supports can give New Zealand children the best start in life.