After "widespread and serious failures" including poor assessment of risk, were flagged by inspectors in 2017, the service is now deemed to be delivering good outcomes for children across all categories.
Chris Munday, executive director of children and young people at the council, was in place during the previous inspection, and has led the turnaround, with support from Essex County Council.
In January 2018, the Department for Education appointed Essex County Council to be the improvement adviser to Barnet Council following an independent review by commissioner Frankie Sulke.
Previously, Essex had provided improvement support in Barnet in 20016 and 2017.
The judgment, published today, states: "The executive director and his team, together with strong corporate support, have ensured a focus on continuous improvement.
"This is underpinned by a clear oversight of practice and comprehensive knowledge of the service."
Strong partnerships have also led to an "effective and well-integrated early help service".
The report notes that partner organisations also have a good understanding of thresholds when making referrals - something that was criticised in 2017 for being "inconsistently made" and "misunderstood at all levels of intervention".
Children who need help and protection are also receiving help and support that is "timely and of good quality".
Assessments and plans show careful consideration of the views of children and their families, and children in care receive a good service from workers who know them well.
Carers provide stable homes and are supportive and ambitious for the children in their care, and care leavers are mostly well supported and have access to a good range of suitable accommodation.
"Staff are tenacious and determined in working with young people to improve outcomes, which they do with care and sensitivity," adds the report.
Munday said he was "delighted" with the findings, adding: "Moving forward, we are clear that working together to drive improvements for our children and young people remains the highest of priorities."
Councillor David Longstaff, chairman of the children, education and safeguarding committee at Barnet Council, said: "The inspection result represents the huge amount of work that has gone into driving improvements for children and young people across the board over the last two years.
"I have every confidence that we will continue to go from strength to strength."