Childcare teams are under "enormous pressure" to cope with the number of children entering care, according to a council report.
The number of children looked after by the county council in Blaenau Gwent rose from 134 in 2013, to 222 on 1 January 2018 - a 66% increase.
By February this year, the figure had risen to 236 children in council care.
The £2.3m budget for child care was likely to be overspent by £942,117 this year, said the report.
The document, due to go before the council's social services scrutiny committee on 12 April, said that since April 2016 staff had dealt with increased workloads and a rise in absences due to stress at work.
The report said: "The child care teams have for some considerable time been working under enormous pressure.
"This is borne out by sustained increase of looked after children, the number of children on the child protection register and the number of referrals received by the department."
Funds for children's residential placements are expected to fall short by £466,059 in 2018, compared with a £1,678 overspend at the end of 2017.
The increased number of placements and the complexity of care needs have been blamed for the shortfall, which is predicted despite increased funding.
Blaenau Gwent council plans to employ three additional social workers until April 2019 to ease the pressure, and a Supporting Change Team formed in January has already worked with 34 children across 20 families.
The report estimated that just two successful interventions completed by the team this year could in the long run save £68,305 for the council.